The invention relates to a method for preparing thieno[3,4-B]-1,4-dioxin-2-methanol. The method comprises the following steps: adding dimethyl 3,4-dihydroxythiophene-2,5-dicarboxylate, 2,3-dibromo-1-propanol and an organic amine catalyst into an organic solvent for heating reaction, and carrying out post treatment to obtain dimethyl 2-hydroxymethyl-2,3-dihydrothieno[3,4-b]-[1,4]-dioxin-5,7-dicarboxylate; adding the dimethyl 2-hydroxymethyl-2,3-dihydrothieno[3,4-b]-[1,4]-dioxin-5,7-dicarboxylate into an organic solvent for dispersion, then adding Lewis acid, water and vanadium oxide or a supported catalyst thereof, carrying heating and stirring for reaction, and carrying out post treatment to obtain thieno[3,4-B]-1,4-dioxin-2-methanol. The method for preparing thieno[3,4-B]-1,4-dioxin-2-methanol, provided by the invention, has the advantages of short reaction route, high product yield and low cost.