A heat sink and power battery system are provided. The heat sink includes a heat dissipation plate and a cover plate. The heat dissipation plate includes a bottom plate and a plurality of fins arranged on the bottom plate in a comb-like pattern. The cover plate is fixedly connected to the heat dissipation plate. The fins of the heat dissipation plate are disposed between the bottom plate and the cover plate, and an air duct is formed among the bottom plate, the fins, and the cover plate.