The invention relates to a preparation method of C2ZnSnS4 sheet-shaped films. The method comprises the following steps: adding 1-4mmol of stannous chloride dihydrate and 1.5 to 8mmol of thioacetamideinto a bottle filled with 200ml of deionized water; regulating the pH value of a solution to reach 0.2 to 1.0; enabling FTO (Florine Transparent Oxide) which is washed cleanly to be put into the solution by vertically adjoining against the cup wall; putting the solution into a constant-temperature magnetic stirrer to carry out reaction for 0.5 to 2 hours at 80 to 90 DEG C; taking out FTO to obtainSnS nano-sheet films, and then cleaning and drying; subsequently, putting 0.8 to 1.2mmol of copper sulfate pentahydrate, 0.025 to 0.04 mmol of zinc chloride, 4 to 6mmol of thiourea, well-grown SnS and 15ml of deionized water into a reaction kettle; then carrying out reaction for 10 to 12 hours at 180 DEG C; cooling, cleaning and drying a reactant; carrying out annealing through nitrogen to obtainthe C2ZnSnS4 sheet-shaped films. The preparation method disclosed by the invention has the advantages of greenness, environmental protection, and simple operation; a precursor is low in material cost, and the prepared films are in sheet-shaped particle shapes and are uniformly distributed, so that improvement on the current-illumination characteristic of the film is facilitated.