Due to the uncertainty in assembly system，manufacturer always likes to implement a delay payment on his suppliers in purpose of mitigating the risk of late delivery caused by any supplier． However，suppliers prefer the on-time payment． Both two payments contracts are well used in practical applications whereas rarely emerged in academic research． And in this paper，we investigate how these two payment contracts affect sup-pliers’and manufacturer’s decisions，as well as the overall performance of supply chain when the production lead time of suppliers are assumed to be stochastic． By analyzing a decentralized system with two suppliers and one manufacturer when both suppliers have a particular stochastic component’s production time，we not only find out the optimal production reserve time for suppliers and optimal buffer time for manufacturer under two payment contracts，respectively． More important，the proper choices of payment contract for manufacturer and supplier under a certain condition are presented． Also，by comparing the supply chain performances between centralized and decentralized system，we also got the conditions under which coordination is achieved while participation constraints meet．