Abstract: In order to improve the efficiency of photobiological effect of skin diseases and solve the problem of low irradiance of phototherapy devices, based on the principle of photobiomodulation and photodynamic action and its clinical application, a multi-wavelength skin phototherapy device with functions such as acne treatment is proposed. By using TracePro for optical system design and simulation, as well as the hardware circuit design for LED light source, the light energy is concentrated and uniform, the irradiance of light is improved, and different light wavelengths and light energy can be combined freely. The test results show that the light of phototherapy device on the target plane is concentrated and uniform, and its total irradiance is more than 50.5 mW/cm².