When the environment and structure of supply chains are stable， the knot enterprises of the chains adjust their operating strategies in order to meet demand. Considering the demand-supply structure and features of a supply chain network based on multi-level suppliers and multi-product intensively operated by a core enterprise， the authors analyze the characteristics of the demand of every knot in the network， obtaining the optimum stock cost when the order fulfillment lead-time is random， and make suggestions on the operating strategies of the supply chain according to the critical service level of every knot and the convex function features of the stock cost.