Abstract: This experiment was aimed to explore the effect of Astragalus polysaccharides （APS） on serum biochemical indexes of lactating Holstein cows.According to the similar age，parity and weight，40 Holstein cows in lactation period were selected and randomly divided into four groups with 10 cows in each replicate in a single-factor completely randomized block design.Group Ⅰ was the control group which fed with basal diet without APS，groups Ⅱ,Ⅲ and Ⅳ were fed basal diet supplement with 10，50 and 100 g/（cow·d） APS，respectively.The experiment lasted for 20 days.The results showed that with the increase of the APS level，the serum activities of ALT，AST，γ-GGT，ALP，CK and the serum contents of TBIL，DBIL，BUN，CRE，CHO，TP，ALB and GLU in groups Ⅱ,Ⅲ,Ⅳ were no significant differences compared with the control group （P＞0.05）.With the increase of the APS level，the serum content of TG in groups Ⅱ,Ⅲ,Ⅳ had a decreased tendency,and 10 days after using medicine,it was significantly decreased compared with the control group （P＜0.05）.In conclusion，feeding the cows with recommendatory dosage of APS in the actual production condition was safe and reliable.10 times as the recommendatory dosage of APS was also safe，and APS was able to regard as a security antioxidant and immunopotentiator in cow breeding.

Key words:   Astragalus polysaccharides；cows；lactation period；safety