The activities of five enzymes in lenses of normal rats, and ratss with galactose induced cataract or galactose cataract feeded with Chinese medicinal herbs were studied. Results showed that in the lenses of galactose cataract, the activity of aldose reductase increased significantly, those of polyol dehydrogenase, hexokinase, 6-phosphate glucose dehydrogenase and catalase decreased. When the decoctions of Scutellaria baiaalensis G.,Dendrobium nobile Lindl, Cuscuta chinesis Lam and Orox-yleum indicum Vent were seperately given to treated rats by intragastric administration at the sametime of galactose induction, the activity of aldose reductase did not increase significantly in the lenses and those of polyol dehydrogenase, hexokinase, 6-phosp-hate glucose dehydrogenase and catalase remained nearly at the normal levels. Thus, it is obvious that the four Chineses medicinal herbs can more or less prevent the abnormal changes in activity of certain enzymes which are concerned in the carbohydrate metabolism or oxidation system of lens, and thus delay the formation of cataract induced by galactose.