Abstract: Effects of nitric oxide (NO) on the antioxidant enzymes of postharvest tomato fruit were investigated in this study. Tomato fruits harvested at mature green and pink stage were fumigated with 20, 40, 60μL·L-1NO, then stored at 16℃ with 85% relative humidity (RH) for 20d. Changes in these levels of superoxide dismutase (SOD) , peroxidases (POD) , catalase (CAT) and ascorbate peroxidase (APX) , respectively, were measured during storage. Results indicated that NO treatment induced the increase in the activities of SOD, POD, CAT activities of tomato fruit at mature green and pink stage. NO treatment induced the APX activity, reduced MDA content, and delayed the losing of soluble sugar of tomato fruits at mature green stage. The concentration of60μL·L-1NO had the better effect on tomato fruits. However, there was no significant influence on the APX activity and MDA content of tomato fruits at pink stage.