Abstract: In recent years, emergency events such as nature disaster, terror attack etc. occur frequently, they affect the normal operation of enterprises and supply chain tremendously. Thus, this question leads to a wide attention about how to coordinate the supply chain to response to disruptions. In reality, because of the knowledge monopolization, industry barrier or benefit conflict, the asymmetric information between the retailer and the manufacturer is existed throughout, and the asymmetry of information is one of the causes which leading to the supply chain's low efficiency. The study motivation and origination of the paper is that the strategies on how to response the disruption under asymmetric information are explored so as to enhance the efficiency of the supply chain by studying the disruption management of the supply chain under asymmetric information.In this paper, a two-stageclosed-loop supply chain composed of one manufacturer and one retailer is considered, while the disruptions cause the stochastic market demand distribution function and the manufacturer's production cost fluctuated simultaneously, how we should use the buy back contract to coordinate the supply chain under asymmetric information to response to the disruption.The paper's study method is to setup aclosed-loop supply chain coordination model under asymmetric information based on buy back contract firstly. As the disruption may affect the supply chain production plan and furthermore it would cause the manufacturer to adjust the production quantity, yet, the production quantity adjustment need to throw in deviation cost, so in the emergency environment, we setup a supply chain model based on a buy back contract by drawing (leading) into deviation cost. In addition, we analyze the model thoroughly. Basing on the retailer's facing asymmetric information of its selling costs and stochastic market demand, firstly the decentralized system decision situation under basic state, and solve the problem of asymmetric information is solved by designing variable parameter anew and realize the information sharing under buy back contract and perfect coordination of the supply chain. Then, the problem of coordination with buy back contract under disruption are studied.The study results show that the supply chain can be coordinated by adjusting the order quantity when stochastic market demand distribution function and production costfluctuated simultaneously. Furthermore, the study finds that only the adjusted option contract can coordinate the supply chain while the origin option contract can't. Thereby the paper testifies that it is effective and essential to coordinate the supply chain by adjusting the option contract while disruptions occur. The study results show that the origin production plan and the buy back price of the manufacturer have a robustness zone when stochastic market demand distribution function and production costfluctuated simultaneously to a small extent as for the closed-loop supply chain under asymmetric information, it is the optimal decision for the manufacturer to keep the original production plan and the original buy back contract in the zone. If the production cost doesn't fluctuate in the zone, the optimal wholesale price can keep unchanging. When the degree of the fluctuation exceeds the robustness zone, the closed-loop supply chain can achieve the optimal profit in the situation of disruption only if the original production plan, original wholesale price and the original buy back contract are adjusted relatively. The study also show that the taking-back activity of used products is not affected by an emergent event. So, while the emergent event occurs, the taking-back strategy of the used products needn't to be adjusted at all.In the part of data emulation and analysis, we design a living example according to the feature of the short life cycle two-stage supply chain, furthermore, we analyze the influence suffered by product quantity, wholesale price and buy back price in the closed-loop supply chain while stochastic market demand distribution function and production cost fluctuated simultaneously caused by the emergent event. By the numeral example, we test and verify the validity of the model on response to the disruption.In brief, this study offers a fundamental train of thought and a frame for coordinating theclosed-loop supply chain under asymmetric information to response to disruptions to the other related researches, moreover, it can be used for reference to the other related studies in how to lead the buy back contract into coordinating the supply chain under asymmetric information to response to disruptions.

Key words: asymmetric information, closed-loop supply chain, emergent event, buy back contract, coordination