Abstract: A new synthetic approach to 2,3,4,4'-tetrahydroxybenzophenone was described. By means of pyrogallol and 4-cyanophenol as raw materials and diethyl ether as solvent, Hoesch reaction was carried out in the presence of HCl and ZnCl2 . Finally, 2,3,4,4'-tetrahydroxybenzophenone was synthesized. Influences of reaction were studied by orthogonal test method. The optimum process conditions were as follows: reaction material proportion of pyrogallol to 4-Cyanophenol 1:0.96(mol:mol),dosage of catalyzer 54.4 g(1 mol pyrogallol comparatively),reaction temperature 20 ℃ and reaction time 24 h.The yield of 2,3,4,4'-tetrahydroxybenzophenone was over 90 % and the product purity was over 98 % under this condition.