The invention provides a plant growth light with a high-efficiency high-power LED as a light source, which comprises a support, a constant-current power source, a control circuit and an LED light source. The LED light source adopts 1 to 10 red light LED light-emitting diodes and blue light LED light-emitting diodes of between 1 and 5 watts and is formed by packaging of red and blue single chips or composite chips, the LED light source is adhered on an aluminum-based printed circuit board through a high thermally conductive adhesive, the center of the LED light source is provided with a light-emitting lens, the aluminum-based printed circuit board is fixedly connected with a flat panel radiator, and two sides of the flat panel radiator have high-efficiency reflecting shades. The plant growth light has low power consumption, long service life of the light source, higher light efficiency and good application prospect, and is capable of effectively controlling illumination required by the plant growth and controlling optical wavelength, duty ratio and frequency quantitively.