The invention discloses a capacity optimization and auxiliary peak regulation method for a regional wind power plant group energy storage power station. The method comprises the steps that 1, a BESS (battery energy storage station) composite function charging and discharging realizing method of wind power plant group power fluctuation stabilization and power network peak regulation is considered, and a capacity optimization calculating model is built by using the BESS operation cost minimization as a target; 2, the super-short-term wind power is utilized for predication, and a real-time optimization operation model is built by using the maximization of gains when the BESS synchronously participates in the power fluctuation stabilization and the power network peak regulation as a target; 3, the cost sharing and gain distribution mode and method of the BESS system operation are provided. Through the adoption of the technical scheme, an energy storage system with the configuration required by a regional wind power plant can be planned, the economic and reasonable energy storage capability is optimized and calculated, meanwhile, an prioritization scheme that the energy storage system participates in the power network peak regulation in an auxiliary way is provided, and the reasonable and efficient operation level of a regional wind field configuration energy storage system is improved.