Based on the institution-based view and the panel data from 2008 to 2013 of 16 listed commercial banks in China, this article makes an empirical study on the relationships among interest rate institution changing, diversification strategy and bank performance by establishing diversification strategy analysis frame of “institution-behavior-performance” specification. Results show that the diversification of commercial banks and the marketization degree of interest rate are positively correlated, and the changing of interest rate institution based on the main feature of interest rate marketization influences the diversification decisions of commercial banks. Moreover, in terms of the changing of interest rate institution, the interaction of interest rate marketization and diversification strategy imposes a significantly positive effect on bank performance.