A Mie scattering radar system with a white light-emitting diode (LED) light source is proposed for the multi-wavelength detection of atmospheric aerosols. By splitting the continuous spectrum, the multi-wavelength echo signals are extracted to achieve multi-wavelength real-time detection of atmospheric aerosols. The white LED spectrum characteristics are analyzed, and four detection wavelengths are set at 450, 525, 600, and 661 nm. The composition and detection principles of a white LED light source radar system are expounded, the design of each system part is described in detail, and the system parameters and data inversion algorithm are presented. We built a white LED light source radar system and conducted preliminary observation experiments. The results show that radar can achieve multi-wavelength real-time detection of atmospheric aerosols within a 300 m height, which can provide effective data for further study of aerosol particle distribution and lay a foundation for further studies of aerosol characteristics at special wavelengths.