The invention discloses a capacity optimization configuration method for a hybrid energy storage system orientating optimization operation of a power distribution network. The capacity optimization configuration method comprises the steps of obtaining imbalance power between the optimal output and photovoltaic actual output when an optical storage system participates in operation of the power distribution network firstly, taking the imbalance power as a hybrid energy storage reference power, adopting ensemble empirical mode decomposition to decompose the imbalance power into a series of intrinsic mode functions, and performing recursion Hilbert conversion to obtain an instantaneous frequency-time curve of each intrinsic mode function separately; according to power type and energy type energy storage characteristics, determining crossover frequency by taking least aliasing of the instantaneous frequency-time curves as a principle, and stabilizing the high-frequency components and low-frequency components of the imbalance power by adopting power type energy storage and energy type energy storage respectively; and finally, by considering charging-discharging efficiency, state of charge and life cycle cost, a power type and energy type energy storage rate power and rate capacity economic optimal configuration scheme is proposed. Compared with a conventional method, new energy output can be compensated, consumption capability to new energy can be improved, and active participation to the optimization operation of the power distribution network can be realized.