The invention relates to a method for preparing a ZnS/SnS double-layer membrane of a solar cell by a vacuum evaporation method, which belongs to the technical field of preparation technology for inorganic membrane elements of solar cells. SnS of a P semiconductor is taken as an absorbing layer, a vacuum evaporation system is used and the double-layer membrane is obtained by continuously evaporating a ZnS membrane and a SnS membrane on different boats. A sample holder is adjusted; the temperature of an indium tin oxide (ITO) glass substrate is controlled to be between 150 and 160 DEG C; the vacuum pressure is between 2*10<-3> and 3*10<-3>Pa; the distance between the substrate and an evaporation source molybdenum boat is about 20 centimeters; the evaporation temperatures of the SnS and the ZnS are controlled to be between 1,000 and 1,200 DEG C; after an evaporation process is finished, annealing is performed in a vacuum tubular annealing furnace; and the annealing temperatures are 300 DEG C, 400 DEG C and 500 DEG C. The method of the invention has simple process and high membrane preparation efficiency; and the prepared membrane has high electrical performance and optical performance and is applied to the solar cells.