Abstract: Effects of molybdenum application on respiration enzymes: polyphenol oxidase(PPO),ascorbic acid oxidase(AAO),glycolic acid oxidase(GO) of vigorous leaves in winter wheat(Mo efficient cv.97003 and Mo inefficient cv.97014) were investigated at tillering stage,jointing stage,heading stage and filling stage.The results indicate that in Mo-treated winter wheat,the activity of PPO decreased in all the four stages;the activity of AAO decreased in the tillering stage and the jointing stage but increased in the heading stage and the filling stage;the activity of GO decreased in the tillering stage,the jointing stage and the heading stage but increased in the filling stage.Differences in responses of activity of molybdenum on respiration enzymes were observed in different molybdenum efficiency winter wheat.Molybdenum application inhibited respiration of winter wheat in the tillering and jointing stage,which was beneficial to carbohydrate accumulation and increased the biologic yield of winter wheat.In the heading and the filling stage,the effect of Mo application on respiration enzymes activity had a big variety.From the tillering stage to the heading stage,the activity of GO decreased when molybdenum was applied,indicating molybdenum application inhibited photorespiration of winter wheat.Therefore,it can increase net photosynthetic rate,and promote carbohydrate accumulation.