Abstract: Objective]The objective of the present study is to investigate the influence of castration on serum protein metabolism,energy metabolism and antioxidant index on Simmental cattle.[Method]50 healthy Simmental cattle (16 month)were used in a paired design of single factor by body weight.[Result]The results showed that the content of creatine kinase in the castrated group was lower than uncastrated group and there were significant difference(P<0.05).The contents of urea nitrogen and albumin in castrated group were higher than uncastrated group by 5.63;and 2.59;,respectively.The difference were extremely signif-icant (P<0.01).The ratio of albumin and globulin in the castrated group was significantly higher than un-castrated group(P<0.05 ).As for SOD,GSH -PX and MDA,there were no difference in the castrated group and uncastrated group (P>0.05).[Conclusion]The results suggested that the castration slows down the metabolic oxidation process,slows down,and steers become gentle and the relative reduction in the a-mount of activity,thus resulting in the body's demand for ATP.Serum creatine kinase and lactate dehydrogen-ase activity decreased,and so did blood glucose consumption;The blood sugar level in serum relatively went up.The assimilation of protein decreased,and the oxidative stress of blood became lower.And the increase in albumin may suggest that ovariectomized cows need more lipoprotein fatty acids and other nutrients.