Various relationships between price changes and trading volume in China stock market were empirically examined. Principles of information economics were applied to analyze the empirical results. The paper showed that the asymmetric volume-price change relationship existed in China stock market, and the linearly positive correlation was inaccurate to describe the relationship between stock price changes and trading volume. The relationship between price volatility and expected trading volume,and that between price volatility and unexpected trading volume were tested．The impacts of information on the stock market were studied ．The results obtained gave meaningful insights into the microstructure of China stock market and were helpful to regulate financia1 market activities．