Net interest margin (net interest Margins (NIM) is the trade bank loans deposit interest rates higher than receiving the deposit interest rates and spending the definition for the ratio of Bank net interest expenditure and average interest earning assets. Net interest margin is bank profit important origin, is also a measure of a bank as a financial intermediary cast intermediary effect is one of the main goals, is the net profit difference not only response to the bank operation efficiency and also response to the bank as a social direct financing of the main intermediary business Wu Benqian and the intermediary potency. Based on the model Ho&Saunders business and Maudos&G.uevara business expansion model basically, based on the bank itself, industry growth and micro identity identity to analyze Chinese in interest control under the background of China's adoption of resolution spreads as the 78 trading banks in 2005-2012 non balanced panel data covering large banks, stock trading for trade, local city commercial banks and rural commercial bank, through the process of using the coherence of target, adopt random effects regression model on the net interest margin of China's commercial banks as resolution of the empirical analysis, and expand the analysis of net interest margin of different types of bank resolution identity differences and the impact of the financial crisis impact on the occurrence of net interest margin resolution identity differences. The important content of study is as follows: the first chapter is the introduction. The Department of the research background, the significance of the topic made specific explanation, and introduces the research framework of this thesis, is initially put forward the innovation points of this thesis. The second chapter is the literature review. The department specific introductions to the current foreign relatively popular two kind of research model and the growth of innovation, and summed up the research of two aspects, initially on the literature stopped briefly review. The third chapter analyzes the international comparison of commercial banks in China growth situation and spreads the identity resolution. The market maker model based on combined with the reality of our country, analyzes the status of China's commercial banks net interest margin resolution and practical assumptions. Chapter 4 is the important focus of the Department, that is, the application of bank data study and hone net interest margin on the resolution of the identity (i.e., application of collecting bank data of our country Commercial Bank net interest margin resolution identity stop empirical research. Through the process of the whole sample stop regression, analysis of the our country commercial bank's net interest margin resolution status and influence; from the regression results of impact on net interest margins compared to Nianye identity hidden accrual of pay, interest rate risk, risk avoid level, credit risk, management effectiveness, business scope, microeconomic variables GDP increased rate and Tonghua contraction etc.. The fifth chapter further expand our analysis of different types of commercial banks and the impact of financial crisis on the net interest margin of identity difference resolution. In terms of different types of banks, net interest margin of the resolutions of the identity of the key differences, in addition to the risk aversion level, governance effectiveness have influences on the net interest margin of four categories of banks outside, large banks was credit risk, implicit interest pay, shake the market interest rate, inflation rate and other factors influence; share-holding system bank was recessive accrual of pay, operating costs, inflation rate and other factors influence; city commercial banks except by GDP increase rate, other resolutions of the identity and the joint-stock banks is consistent; commercial bank also was the opportunity cost of reserves. The financial crisis that have an impact on net interest margin resolution identity, from the regression results can be seen, commercial bank's net interest margin was risk aversion level, management effectiveness, the influence of implicit interest payments and reserve opportunity cost, but the impact of different level, medium risk avoid pay levels and hidden cost affects the level of change Nianye, and governance effectiveness and reserve opportunity costs affect the level of decline. The sixth chapter summarizes this research conclusion summary, then put forward some policy suggestions. According to the empirical results of the analysis, the author think that China's commercial banks to continuously improve the level of management, strengthen cost control; optimization of the traditional business, the central business growth and progress of market power; strengthen deposit mechanism, perfect risk management. Banks should be strengthened governance, according to the identity of the different resolution difference and their search of the strengths and advantages of ceases to grow and fill. The innovation of the important expression in the following aspects: (1) in the empirical approach, and the mostly used in the research fixed effects model differences, the color with modification of the random effect model to research our country Commercial Bank net interest margin on the resolution of the identity. From a statistical perspective using random effects model will prevent the loss of freedom. From the economic point of view, this paper think that every bank has its own characteristics (for example, cultural differences, etc.) is the existence of individual effects and time effects, and the interest rate is coherent shake. Comprehensive analysis and statistics practice, this paper will take the identity resolution random effect model to study the net interest margin. (2) the research object is more comprehensive, more fruitful data origin. This research covers the state-owned banks, joint-stock banks, city commercial banks and rural commercial four varieties, more comprehensive choice of the object of study and discussion of the differences in the type of the bank's net interest margin resolution identity difference. In contrast, previous studies have little choice of city commercial and agricultural firms, agricultural firms are special. On the origin of data, previous international scholars take listed banks maybe a few a few unlisted bank data, the data missing department take historical data imitation may direct the sample excluded and reach the balanced panel data. And the application of BANKSCOPE compared to perfect the database, select the raw data of 78 commercial banks from 2005 to 2012 the non disposing non balanced panel data, provides a more perfect and more real sample data for research, to fill the lack of in the international. (3) the change of net interest margin of China's trade status on 2008 bank resolution before and after the financial crisis, will help in the future with useful way to deal with the crisis. The previous literature is an important analysis before and after the transformation of China's interest rate difference, but there is little effect of depth discussion of the 2008 global financial crisis on bank spreads. In view of this, this paper in 2008 the financial crisis as the cut-off point, focusing analysis before and after the crisis in our country commercial bank's net interest margin resolution identity change, coherent conclusion of the study will be beneficial to the Commercial Bank of our country in future encounter sudden micro economic shake, can better mining methods, useful system to deal with risk.