The invention discloses an electric car power system control device. The device comprises a box shell, a cooling plate, a DCDC module and capacitor assembly, a plurality of module assemblies and a winding displacement interface, wherein the box shell is internally provided with a cavity; the cooling plate is mounted in the cavity to divide the cavity into a cavity upper layer and a cavity lower layer; the DCDC module and capacitor assembly is mounted in the cavity lower layer and leans on the cooling plate; the plurality of module assemblies are mounted in the cavity upper layer and lean on the cooling plate; and the winding displacement interface is mainly mounted in the cavity upper layer and is configured to provide an interface for connecting the other module assemblies. The device integrates core components of electric cars; and compared with the prior art, the device is compact in structure, small in volume and convenient to mount and maintain, and has relatively high practical value and popularization value.