The inductively coupled plasma atomic emission spectrometry method has been used to quantitatively detect P2O5content in water soluble fertilizer by screening suitable analyticallines，it avoids the problem of low results caused by incomplete hydrolysis. The P2O5concentrations have a good linear relationship(r 2=0.9998)in the range of 0.00～200.0 mg/L，the relative standard deviation(RSD)is 0.25%～0.47%，and the recoveries are 97.92%～ 102.0%. The limit of detectionis 0.002 8%.Meanwhile，the results are compared with those of quinoline phosphomolybdate gravimetric method，which shows this method can meet the requirements of real sample analysis.