Abstract: The aims of this study were to determine the antioxidation protective effects of vitamin E on the quality of straw frozen semen and antioxidant enzyme activity in seminal plasma of Qinchuan cattle. In this experiment, the vitamin E with different concentrations (0.00, 002, 004, 0.06, 0.08, 0.10 mg·mL1) were added in the ordinary dilution. After thawing the straw frozen semen(37.5 ℃,30 s), the motility of sperm, the integrity rate of sperm acrosome and other parameters were analyzed by WEILI sperm analysalor. Then the activity of SOD, GSH, GR and CAT were detected by the related kit. The results showed that when the addition of vitamin E was 0.04 mg·mL1, there were significant differences between experiment and control groups in motility of sperm (P<0.05) and also had significant differences in enzyme activity of SOD, GSH and CAT (P<0.05). When the addition of vitamin E was 0.06 mg·mL1, the motility of sperm were significant higher than that of control group, the integrity rate of sperm acrosome was significant higher than that of control group (P<0.01); there were significant differences between experiment and control groups in the activity of GR and CAT. When the vitamin E concentration was 0.08 mg·mL1, the sperm motility, the motility and the integrity rate of acrosome had very significant differences (P<0.01) between experiment and control groups, there were significant differences in GR and CAT activity between experiment and control groups. With the addition of vitamin E in the dilution of frozen semen, the quality of frozenthawed semen and enzyme activity of SOD, CAT, GSH and GR in seminal plasma of Qinchuan cattle can be effectively improved, and the appropriate additions of vitamin E in ordinary dilution were 0.040.08 mg·mL1.