Abstract: Based on the improvement of the market maker model, and using the unbalanced panel data of 101 commercial banks from 2005 to 2015 in China, this paper studies the combined impact of interest rate liberalization and non-interest income on net interest margin of banks with the method of dynamic panel GMM. The results show that: 1) In general, interest rate liberalization has a significant negative impact on net interest margin of commercial banks. Among them, the impact on local banks is the biggest, and the impact on joint-stock banks is the second, while the state-owned banks are the least affected. 2) Both non-interest income and classified non-interest income have a significant negative impact on net interest margin of commercial banks. With the increase of the degree of interest rate liberalization, the negative impact is further enhanced. 3) Classified non-interest income impacts net interest margin of commercial banks in different paths. The main effect of fees and commissions is “cross subsidy effect”, while the main effect of trading income is “resource substitution effect”. 4) For state-owned banks and joint-stock banks, income from fees and commissions has a significant negative impact on net interest margin, but the impact of trading income on net interest margin is not significant. 5) For local banks, income from fees and commissions and trading income both have a significant negative impact on net interest margin. On this basis, this paper analyzes the reasons for the difference and makes reasonable suggestions for all kinds of commercial banks and regulators.

Key words: Interest Rate Liberalization, Non-interest Income, Income from Fees and Commissions, Trading Income, Net Interest Margin