In this paper,we theoretically analyzed the relations among information,noise,the volatility of stock price and the synchronicity of stock price from the viewpoint of financial economics.We put forward a hypothesis that there is an inversely U-shaped relationship between the informativeness and the R2.Our empirical results show that the above hypothesis is proved to be correct by using the trading data of A-share stock market of our country in 2004,with the ratio of shares which are hold by inst...