The invention provides a preparation method of a copper-indium-zinc-selenium film of a photovoltaic battery for a photovoltaic power generation system. The copper-indium-zinc-selenium film comprises the following components: 20.55-20.59% of Cu, 25.54-25.60% of In, 15.62-15.68% of Zn and 38.10-38.19% of Se, wherein the sum of the percents of the components is 100%. The preparation method comprises the following steps: 1) preparation of an electrodeposition solution, namely preparing the electrodeposition solution from deionized water at normal temperature, and regulating the pH value to 2.5-3.0; 2) electrodeposition of a film, namely performing electrodeposition under the conditions that the constant potential is -1.0V, the temperature of the solution is 25 DEG C and the deposition time is 30 minutes, wherein the solution is operated at room temperature without stirring; 3) selenizing treatment of the film, namely putting the film and a molybdenum box filled with 3g of solid selenium into a selenizing furnace, heating to 450 DEG C at a rate of 10-15 DEG C/min, selenizing for 1 hours, and the performing furnace cooling; and 4) heat treatment of the film, namely performing heat treatment at a constant temperature of 350 DEG C for 10 minutes, heating to 550 DEG C at a rate of 15-20 DEG C/min, keeping the temperature for 50 minutes, and finally preparing the copper-indium-zinc-selenium film. The preparation method is low in cost, simple to operate, and is beneficial to requirements for large-area production and environmental protection as well as development and utilization of photovoltaic energy.