An application of the bromophenol compounds chosen from bis-(2,3-bibromo-4,5- dihydroxybenzyl)-ether, 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenyl methane, 2,2',3- tribromo-3',4,4',5-tetrahydroxy-6'-ethoxymethyl diphenylmethane, 3-bromo-4,5-bis-(2,3-dibromo -4,5-dihydroxybenzyl)-catechol, their pharmacologically acceptable derivatives, and their mixture in preparing the depressant of protein tyrosine phosphatase for treating diabetes and obesity is disclosed.