Abstract: This experiment selected phosphorus inefficient varieties MANIC and phosphorus efficient varieties V7,under normal P（1.0 mmol/L KH2PO4）and low phosphorus stress（0.1 mmol/L KH2PO4） two levels,through hydroponic experiments,and the differences of phosphorus efficiency of different oat varieties root secreted acid phosphatase and acid phosphatase activity in different leaves were studied.The results showed that the phosphatase activity of root and leaf secreted by the high efficient oat cultivar V7 and the low efficiency oat cultivar MANIC increased significantly under low phosphorus stress,indicating that the secretion of acid phosphatase in plants was an adaptive mechanism for low phosphorus stress.The activity of acid phosphatase secreted by root and leaf of V7 were higher than that of MANIC,and the difference was significant.The results showed that the utilization efficiency of phosphorus was higher under the condition of phosphorus deficiency.