Abstract: The effect of adding commodity phytase into the laying hens＇ feed to substitute dicalcium phosphate （DCP） with different level was explored and discussed by using the principle of phytase being able to hydrolyze phytic acid in plant feedstuffs. 50 to 54-week-old Hy-line brown laying hens were selected as experiment objects, 400 FYT phytase were added in every 1 000 kg feedstuff to replace 8 g and 16 g of DCP resp. to observe the influence of phytase on the performance of laying hens. The results showed that the performance of laying hens could keep steady by replacing 16 g DCP with 400 FYT phytase, while the performance of laying hens could be enhanced with substitution of 8 g DCP. The daily egg output, laying rate and feed-egg ratio raised 3.4 %, 3.6 % and 3.7 % resp., therefore, the performance of laying hens could be enhanced by replacing 8 g DCP with 400 FYT phytase in the laying hens＇ feed and total phosphorus in feed formula could be reduced as well.