The controversy on financial market validity is continuously conducted and the judgment on the validity of China’s stock market does not attain the goal. From the perspective of emergency event of pollution, through comparison and analysis of the emergency reaction of stock prices in H-share market and A-share market to the momentum of emergency events, this paper examines validity situation of China’s stock market and finds that the reaction extent of H-share is less than that of A-share, which shows that China’s stock market has short-term momentum effect and can reveal current public information to some extent, however, this reaction is not enough, lags behind and does not reach semi-strong form efficiency. Thus, China’s stock market is still in initial stage of development, and the comprehensive factors such as weak company management structure, inadequate government supervision, insufficient environment regulation and so on result in special fluctuations of industry block share prices.