Abstract: The problem that emergency inventory in one supply chain is transshipped by another supply chain nearby(cluster supply chains) is investigated.A system dynamics method is applied to model and optimize across-chain inventory between two retails from two supply chains respectively,and then inventory management is improved by modifying inventory to satisfy the sale period and extending from one echelon emergency transshipment to two and three echelons.The experiment indicates that the average inventory and its fluctuation in cluster supply chains reduce dramatically and customer satisfaction improves under three echelons emergency transshipments.Finally,a hybrid contract is put forward to implement the across-chain inventory emergency transshipment in cluster supply chains.