Abstract: In the experiment 306 newlyhatched Avian broilers were conducted to study the effects of two kinds of phytase substitute inorganic phosphorus in diet on the growth performance, nutrient availability and excretion of feces P and N. 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 34 broilers per pen. The results indicated that ADG and ADFI of experiment group dietary supplementation with phytase were decreased（P＞0.05）; survival rates of broilers and the availability of Ca and P were increased significantly(P<0.05); the utilization of N was improved (P>0.05); and the excretion of N and P for broilers was decreased(P<0.05). the phytase Ⅰ was superior to phytase Ⅱ, diet added with phytase Ⅰ had significantly improved ADG and ADFI (P<0.05),and decreased the excretion of N (P<0.05)，but excretion P had no significant between two groups.

Key words: broiler; phytase; phosphorus; growth performance; nutrient availability; excretion of nutrients