The invention discloses a power battery cooling system based on a core-cladding-structure composite phase-change heat storage layer. The power battery cooling system comprises a system shell, battery unit modules, heat storage modules, an upper cover plate and a lock screw, wherein the battery unit modules and the heat storage modules are distributed in the shell in a layered and staggered manner, and the upper cover plate and the lock screw are used for realizing assembling and positioning; each heat storage module wholly adopts a core-cladding structure and comprises an outer sealing shell and a composite phase-change material, the outer sealing shell is positioned at the outer layer of each module and made of a high polymer material, the inner chamber of the outer sealing shell is filled with the composite phase-change material in a vacuum manner, and the composite phase-change material is formed by mixing a heat conduction material and a paraffin type phase-change material; the curing temperature of the high polymer material is set to be higher than the phase change temperature of the composite phase-change material, and a certain vacuum clearance is retained in the inner chamber of the outer sealing shell made of the high polymer material for the composite phase-change material. According to the power battery cooling system, the heat storage modules which are convenient to operate and control and can circularly charge and discharge heat. Compared with the prior art, the power battery cooling system effectively solves the problems of difficult sealing and expansion pressure likely caused by the phase-change material.