This paper presents a model to describe the dynamic trading process in limit order book.By studying the dynamic pattern of execution probabilities of limit orders with both time and the depth of limit order book,the authors conclude with the following properties:Arrival rates of market buy orders increase as the depth of buy queue in the book increases and decrease as the depth of sell queue increases,and vice versa;similar regularities for the arrival rate of market sell orders;both the arrival rate of market buy order and market sell orders increase as the depth of both sides in the book increases by the same amount.Furthermore,the authors describe more detailed temporary and permanent effects of the market depth on the arrival rates of orders. This paper presents a model to describe the dynamic trading process in limit order book. By studying the dynamic pattern of execution probabilities of limit orders with both time and the depth of limit order book, the authors conclude with the following properties: Arrival rates of market buy orders increase as the depth of buy queue in the book increases and decrease as the depth of sell queue increases, and vice versa; similar regularities for the arrival rate of market sell orders; both the arrival rate of market buy order and market sell orders increase as the depth of both sides in the book increases by the same amount.Furthermore, the authors describe more detailed temporary and permanent effects of the market depth on the arrival rates of orders.