A radiator and a plant illumination lamp containing the radiator. The radiator includes a heat-radiating baseplate configured for fixing a heat source, and heat-radiating side plates connected to the heat-radiating baseplate. The heat-radiating side plates each are provided with a plurality of heat-exchanging through grooves running through the heat-radiating side plates. The heat-exchanging through groove forms a heat potential difference, so that under the influence of the heat potential difference, the cold air outside the radiator passes through the heat-exchanging through groove on the heat-radiating side plates, and then flows out through a hot air chamber and an air outlet at an upper end of the hot air chamber after exchanging heat with the heat-exchanging through groove on the heat-radiating side plates, so as to form a strong natural air convection.