The invention provides a preparation method of metal-doped indium sulfide nanosheets. The preparation method comprises the steps that S1, indium salt, metal-doped salt and dialkyldithiocarbamate saltare mixed and reacted in an organic solvent to obtain a precursor complex; S2, the precursor complex is heated and reacted in an amine solvent to obtain the metal-doped indium sulfide nanosheets. Compared with the prior art, metal doping is introduced into the indium sulfide nanosheets by controlling synthesis and thermal decomposition of a precursor, the preparation process is simple and easy, massive nanosheets can be prepared, the precursor ratio can be controlled, and the concentration of doped ions can be precisely adjusted. The introduced ions have universality, the nanosheets are uniform in thickness and high in dispersibility, and the catalytic activity of the nanosheets in electroreduction of carbon dioxide is improved. By means of the method, the manganese-doped nanosheets are prepared, and moreover, the nanosheets doped with other ions can be massively prepared, and the preparation method is wide in application prospect.