For the restriction relation between energy storage system configuration capacity and battery life attenuation degree and wind power integration demand deviation, the invention provides an energy storage capacity optimal configuration method considering operation and penalty cost. The method is characterized in that the method comprises calculating influence, that is, attenuation coefficient, of different charge and discharge cycle depths on service life of a lithium battery; calculating operation cost of different battery energy storage capacity configurations; and calculating penalty cost of the different battery energy storage capacity configurations and the like. The method, taking factors of system operation cost and the penalty cost and the like and taking lowest energy storage system cost as an object, provides an effective strategy for energy storage capacity configuration. The method has the advantage of being reasonable and scientific, being high in applicability and being good in effect, can enable the energy storage system to realize optimal capacity configuration, and realize low total cost and the like.