The present application provides a preparation method of a gas phase diffusion electrode for electrocatalyzing CO2 to reduce and produce formic acid and an application thereof, comprising: obtaining first mixed solution, obtaining second mixed solution, uniformly mixing the first mixed solution and the second mixed solution, coating them onto a surface of a substrate, and then placing them at a temperature of −30° C.-100° C. for 1-48 hours to obtain the gas phase diffusion electrode. In the preparation method, conductive polymer monomer and bismuth or tin based metal component are coated onto the surface of the substrate to form an integrated conductive polymer-catalyst/hydrophobic substrate composite gas phase diffusion electrode, not only can the stability between metal active components and the substrate material be enhanced, but also characteristics such as better conductivity, higher specific surface area, abundant surface chemical reaction sites, and so on are provided.