This paper investigates the market microstructure of the Shanghai and Shenzhen Stock Ex- changes. The two major Chinese stock markets are pure order-driven trading mechanisms without market makers, and we analyze empirically both limit order books. We begin our empirical model- ing using the vector autoregressive model of Hasbrouck and extend the model to incorporate other information in the limit order book. We also study the market impact on A shares, B shares and H shares, and analyze how the market impact of stocks varies cross sectionally with market capital- ization, tick frequencies, and turnover. Furthermore, we distinguish the market impacts of small, average and block trades, and conclude that the market impacts of small trades are signi?cantly lower than those of other trades.