Due to rejecting order in a single supply chain for lack of adequate capacity, a multi-chain system is introduced to avoid this potential operational risk. Based on four categories of order: direct order, reserve order, chain-to-chain order and rejected order, the framework of order selection in multi-chain system(MCS) is presented, and the model of order selection and planning under chain-to-chain collaboration is formulated. Then, the Lagrange algorithm is used to solve this problem through Lagrange relaxation and decomposition. Finally, numerical study show that opportunity cost of rejecting reserve order and production cost of chain-to-chain order have significant impacts on order selection, and there exists a critical threshold value of the combination of two factors. Through the combination, the multi-chain system can obtain the optimal status, meanwhile manager can utilize this to realize different strategies in MCS. Based on four categories of order: direct order, reserve order, chain-to-chain order and rejected, due to the order of a single supply chain for lack of adequate capacity, a multi-chain system is introduced to avoid this potential operational risk. Order, the framework of order selection in multi-chain system(MCS) is presented, and the model of order selection and planning under chain-to-chain collaboration is formulated. Then, the Lagrange algorithm is used to solve this problem through Lagrange relaxation And decomposition. Finally, numerical study show that opportunity cost of rejecting reserve order and production cost of chain-to-chain order have significant impacts on order selection, and there exists a crisis threshold value of the combination of two factors. Through the combination, The multi-chain system can obtain the optimal status, and the manager can utilize this to realize different strategies in MCS.