Abstract: In this paper, a hybrid renewable energy system containing flexible hydrogen storage and battery storage is proposed, along with a multi-stage co-optimization method for planning and operation. In the first stage, the capacity of WT and PV in the hybrid system is optimized to minimize the net load; In the second stage, a bi-level co-optimization of capacity operation is conducted for the hybrid energy storage system under three typical operating conditions, namely normal operating conditions, extreme full charging conditions and extreme full discharging conditions, where the upper-level model optimizes the storage capacity based on minimizing the cost of levelized cost of storage（LCOS） and the lower-level model optimizes the operation strategy to minimize the power deviation. The optimization problem is solved by a meta-heuristic algorithm coupled with mixed-integer linear programming. The study shows that. 1) When considering extreme full-charge and full-discharge operating conditions, the flexible combination of the components of the hydrogen storage system allows the system to cope with extreme operating conditions more economically, reflecting the superiority of hydrogen storage. 2) The hybrid energy storage system has higher economic efficiency than the single energy storage system, and its LCOS is reduced by 3.97% compared to the single hydrogen storage and 8.25% compared to the single battery storage.3) The multi-stage co-optimization method of planning and operation proposed in this paper reduces the LCOS by 13.7% compared with the rule-based capacity optimization method.