Abstract:   In the existing studies,twotier supply chain with single supplier and single retailer is widely considered.This paper addresses a more complex supply chain with single supplier and two retailers.For such a supply chain,quantity flexibility contract is widely adopted.By using digital analytical method,quantity flexibility contract is analyzed in this paper.Results show that quantity flexibility contract can flexibly coordinate the decision making behavior between the supplier and retailers,and maximize the overall profits of the supply chain.In this way,it provides a basis for the future research on complex supply chain with multiple retailers.