The invention provides a catalyst for preparing formic acid from carbon dioxide by electroreduction and a preparation method of the catalyst, and belongs to the field of electro-catalysis. The catalyst is a chalcogen-doped metal electrocatalyst, chalcogen contains at least one of sulfur, selenium and tellurium, and metal contains at least one of indium, stannum, lead and bismuth. The preparation method comprises following steps: 1), an elementary substance of chalcogen or a compound of chalcogen is dissolved in N,N-dimethyl formamide with metal salts, a carbon material is placed, and a mixtureis transferred into a high-pressure kettle and subjected to solvent heat treatment; 2), after the solvent heat treatment, the carbon material is taken out, washed by deionized water and dried, a carbon material supported chalcogen-doped metal oxide precursor is obtained and then subjected to electroreduction, and the carbon material supported chalcogen-doped metal electrocatalyst is obtained. When applied to the reaction of preparing formic acid from carbon dioxide by electroreduction, the catalyst is high in reactivity, high in selectivity and stable in catalytic performance and maintains high formic acid selectivity in a wide current range.