The invention discloses a fabrication method of a lead sulfide quantum dot. The lead sulfide quantum dot having favorable monodispersity and with a size of about 3-5 nanometers is fabricated by a water-bath heating method. By a lead sulfide quantum dot material, the energy loss of transmission light and long-wavelength incident light can be reduced, the utilization ratio of a solar cell in a whole solar spectral range is improved, and the photoelectric conversion efficiency of the solar cell is further improved. The method is simple, is easy to operate, is low in cost and can be used for fabrication and production in a large scale.