A starch biosynthesis method may implement total artificial biosynthesis from simple compounds such as dihydroxyacetone, formaldehyde, formic acid and methanol to starch. By coupling with methods such as chemical reduction of carbon dioxide, even total artificial biosynthesis of starch taking carbon dioxide as a starting raw material can be implemented. The method can utilize carbon dioxide of high concentration and high density and electric energy and hydrogen energy of high energy density, is more suitable for an industrial production mode, and the production cycle is shortened from several months in farming to several days.