Nowadays there are more and more uncertain marketing factors that the enterprises must face. The enterprise competitiveness depends on a trust-and-collaboration supply chain relationship. It is important to propose a more exible contract based on the traditional contract. Commitment contracts are proposed in this paper, and di erences between the commitment contract and the traditional contract are discussed. A two-echelon supply chain model is introduced under uncertainty. The supply chain members' optimal decisions are gained when the retailer o ers the supplier a commitment contract. Then the paper considers the application of the commitment contract when the supply chain can complement products two times. All our ndings are illustrated by numerical examples.