n this empirical study, we combine the company size style investing with the company booktomarket ratio style investing in the form of composite style investing, and construct the arbitrage portfolios based on momentum return of composite style to illustrate the evolution process of the style rotation effect. Furthermore, according to features of style rotation in Chinese stock markets, we explain the style rotation effect from the adaptive market hypothesis, and point out that the investors will take the corresponding investing styles as the market environment changes, and these adaptive style switching behavior bring about the style rotation effect.