Abstract: Focusing on the two-stage supply chain,in which demand and market price fluctuate randomly,an emergency quantity flexibility contract model under asymmetric information of sale cost was designed using Revelation Principle,in order to find out the optimal ordering and the wholesale price strategy. Meanwhile,the model above was compared with the model under symmetric information to explore the impacts of emergency and the asymmetric information of sale cost on optimal decision of supply chain. Then a numerical example was given to verify the results. The results show that,when emergency causes demand and market price to fluctuate randomly,the supplier can only ensure that retailers share private information by redesigning the contract,but cannot achieve the coordination of supply chain. At this time,the expected revenue of supplier decreases with the increase of information asymmetry. But retailers can obtain more lucrative profits through information asymmetry. If market demand increases,the retailer's behavior of hiding information will inhibit the production increasing plan, and reduce the supply chain profit. Meanwhile,if market demand decreases,the supplier's strategy of reducing supply and wholesale price can effectively prevent oversupply risk.