Abstract: Total glucosides of Picrorhiza scrophulariiflora (TGP)is the active principal in Picrorhiza scrophulariiflora which has antioxidant effect. Since oxidative stress plays a key role in diabetic nephropathy, we investigated the effects of TGP on oxidative stress in bovine glomerular mesangial cells (MC) induced by prolonged high glucose. Bovine glomerular mesangial cells were cultured and passages 2-3 were used for the experiment. Mesangial cells were cultured in high glucose medium, and treated with TGP for 3 weeks. Then collagen IV excreted by mesangial cells were detected, and the percentages of cell cycle were observed by flow cytometry technique. The levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and ［Ca²⁺］_i were measured by flow cytometry after loaded with fluorescent probe DCFH-DA, Rh123 and fluo-3-acetoxymethylest. TGP significantly decreased the excretion of collagen IV and cell hypertrophy induced by high glucose, reduced the levels of ROS and ［Ca²⁺］_i, and increased MMP. Therefore we conclude that TGP could protect mesangial cells against oxidative stress induced by high glucose.