In this paper, we test the policy effect in the stock market and the impact of social interaction on policy effect. The stock market policy is divided into five categories. Based on Sina Finance and Economics Blog, we build variables about social interaction, investor sentiment, and social network centrality by making use of the technology of text mining and social network. Empirical studies show that public opinion-oriented policies have a significant positive impact on stock market returns; securities supply-demand policies and monetary policies significantly increase stock market volatility, and market innovation and market trading policies significantly reduce market volatility. Furthermore, as investors' interpretation of the professional policy is significantly dependent on social interaction, social interaction can magnify the impact of securities supply-demand policy and monetary policy on the stock market, while alleviating the impact of market innovation and market trading policy on the stock market. However, the effect of public opinion policy on the stock market is not influenced by social interaction.