Abstract: In this paper,the storage was introduced into a superstructure-based optimal planning mixed integer linear programming（MILP） model of cogeneration systems.The model can achieve simultaneous optimization of system structure and operation as well as simultaneous optimization of all equipment including storage.At the same time the branch and bound method combined with the simplex method was used as a solution algorithm.Through a case study,the validity and effectiveness of the proposed model and the method were verified.The computational results also indicate that,the introduction of storages in cogeneration systems reduces the capacities of other refrigeration equipment;under time of use electricity rates,storage enhances the system flexibility and economic and energy saving can be obtained through removing some of the strong coupling relationship between cooling/heating demands and generators.The optimal operation strategies of storage are different in typical days,which depend on electricity price,energy demands et al.