中文摘要：

本文考虑由供应商、零售商和消费者所构成的三级供应链系统，其中供应商提供给零售商贸易信用M，零售商提供给消费者贸易信用N，即同时存在上下游贸易信用。在假设：（1）消费者需求同时与上下游贸易信用期限相关；（2）零售商会面临违约风险，违约风险与提供给消费者的贸易信用期限有关条件下，以实现供应商和零售商各自收益最大化为目标，建立模型，分析讨论，给出最优贸易信用期限决策。最后，通过数值算例对理论研究结果进行验证。

英文摘要：

In a supplier-retailer-consumer supply chain, the supplier frequently offers the retailer a trade credit of M periods, and the retailer offers a trade credit of N periods to consumer. Namely, there is a tow-level trade credits supply chain. This paper proposes revenue models for the supplier and retailer where： （1）the demand rate is a positive exponential function of the supplier＇s up-stream credit period and the retailer＇s down-stream credit period, （2）the retailer＇s down- stream trade credit increases default risk. In order to achieve their revenue maximization, we then solve their models and show the supplier＇s and retailer＇s optimal credit periods. Finally, we run some numerical example to apply the conclusion.