Abstract: 【Objective】Thirty Holstein bulls assigned randomly to five groups was conducted to study the effect of different levels of zinc on semen quality and blood biochemical parameters.【Method】This experiment involved 5 dietary treatments, consisting of one control group fed basal diet and four levels of zinc which is 50,80,110,200mg/kg. The experimental period lasted 8 months. 【Results】The results shows that: (1) The effect of different levels of zinc on the sperm motility, ejaculate volume and the sperm concentration was extremely significant(P<0.01); but that on the acrosomal integrity of sperm was not significant(P>0.05); and zinc supplemental could reduce the percentage of abnormalities significantly(P<0.05); (2) The effect of different levels of zinc on the testosterone contents in serum was extremely significant (P<0.01); but that on serum zinc, zinc and testosterone contents in seminal plasma was not significant (P>0.05); (3)The effect of different levels of zinc on the activity of GOT in seminal plasma was extremely significant (P<0.01), but that on LDH was not significant(P>0.05) and which on AKP,GPT was significant(P<0.05); The effect on the activity of GPT、GOT in serum was extremely significant (P<0.01),but that on AKP、LDH was not significant (P>0.05). 【Conclusion】All of the variety of physiological and biochemical parameters analysed in each group indicated that the optimal supplementation of zinc was 110mg/kg by the dry matter in this experiment.