Abstract: Considering the structure of supply chain in practice and Shortcomings of quality control study in four-levels of supply chain present. In this paper, the product quality control problem in four-levels of the supply chain, which consist of suppliers, manufacturers, distributors and customers is studized based on the stackblerg game mode. Considering the uncertainty of customer demand,the variation of the product quality level and supply chain's profit with coordination of initial payment proportion and delay in payment between the manufacturers and distributors are analyzed. Also the optimal quality control levels of the manufacturers and suppliers are solved using the principle of optimization, after the simulation, the result shows:The quality levels of the supplier and supply chain will be affected by the coordination strategies between nonproductive parts indirectly. Whether increase the initial payment proportion or shorten the time of delay in payment, the quality levels of the manufacturer and supplier will be coordinated, especially, the quality level of raw material. However, both of the benefit variations of other subjects caused by quality control and the influence of the consumer demand because of the product market price changes must be considered, when the two strategies are used.

Key words: proportion of initial payment, delay in payment, quality control, four levels of supply chain