Abstract: Abstract：In this experiment fifty-four growing pigs were conducted to study the effects of Escherichia coli phytase and Aspergillus niger phytase substitute Calcium phosphate in diet on the growth performance，nutrient utilization，serum biochemical parameters and excretion of feces P and N for growing-finishing pigs. There were 3 treatments with control group，experiment groupⅠ， experiment groupⅡ， and normal diet was fed to control group，low-P diet adding phytaseⅠwas fed to experiment groupⅠ， low-P with adding phytaseⅡwas fed to experiment groupⅡ. Each treatment had 3 replicates with 6 pigs per pen. The addition of phytase in low-P diet improved ADG，reduced F/G，what is more，supplement Escherichia coli phytase to diet had significantly improved the growth performance of pigs. Adding phytase in low-P diet improved the apparent digestibility of DM，CP，CF，EE，Ca，P，GE respectively (P<0.05). The excretion of feces P and feces N was decreased by fed low-P with adding Phytase diet. The concentration of total protein，globulin，P were improved by adding phytase(P<0.05)，the concentration of BUN，serum Ca was decreased by fed diets with adding phytase (P<0.05). The enzymatic activity of alkaline phosphatase in serum was not affected and the concentration of serum sugar was decreased by adding Aspergillus niger phytase; the enzymatic activity of alkaline phosphatase in serum was decreased (P<0.05) by adding Escherichia coli phytase.

Key words: Key words：growing piglet; phytase; growth performance; apparent digestibility; serum biochemical parameters