The coordination problem of the manufacturer dual channel supply chain was analyzed. Introducing two variables of the dual channel price sensitive coefficient and the competition coefficient, and assuming that the retailer's cost information is the private condition, the optimal response of a dual channel supply chain on unexpected events under asymmetric information was studied. The results show that the supply chain optimal production quantity, optimal selling price, wholesale price and optimal retail price have certain robustness. In the asymmetric information situation, the emergency causes the cost of the retailer to be disturbed in a certain range, and the optimal production plan of the double channel supply chain can be kept unchanged. But when the cost disturbance of the retailer exceeds a certain range, coordination is needed in order to make the supply chain rebalance and realize the effective response on the emergency. The conclusions in the paper were verified by numerical simulations.