Abstract: Nowadays, the incidents often occur that retailers terminate the cooperation with their suppliers. Retailers' exiting the supply chain will not only cause loss of profits to itself and the suppliers, but also have shocks on basis the of supply chain cooperation.In this paper, whether the supply chain need to cooperation to cope with the problems when it has retailers' exiting risk is studied. The coordinated supply chain with quantity discount contract as the research foundation is chosen. By judging the adaptability of traditional quantity discount contract in the supply chain with retailers' exiting risk, the improved quantity discount contract which can coordinate the supply chain with exiting risk is then introduced. A two-level supply chain with one supplier and one retailer is built.Through the theoretical analysis and the numerical simulation of centralized and decentralized decision-making of the the model, it is found that retailers' exiting risk may have the great shock on the supply chain operations.At the same time, it is surprisingly found that although the quantity discount contract can not coordinate the supply chain under the great shock, the efficiency is very high. Therefore, it is suggested that in the supply chain with retailers' exiting risk, if the cost of coordination between the retailers and suppliers is very high, they can still use the traditional quantity discount contract contract since in this case it can achieve higher efficiency. But if the cost of coordination between enterprises is lower than the benefits the coordination brings, it is more beneficial to retailer and suppliers to adopt our recommended quantity discount contract.

Key words: retailer's exiting risk, supply chain cooperate, supply chain coordination, quantity discount contract