At present, more and more phosphorus is entering the water, which seriously affects the ecological environment and human health, however, the traditional methods of phosphorus analysis are complex and require multiple reagents. In this paper, total phosphorus in water is determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). In this paper, the instrument working conditions were discussed. The results showed that the optimum instrument working conditions were as follows: the analytical line was 213.617 nm, the RF power was 1 300 W, the nebulizer flow rate was 0.5 L·min-1, the observation height was 15 mm, the peristaltic pump speed was 1.2 mL·min-1, and the observation way was radial. Under the optimum working conditions, the detection limit, precision and recovery of phosphorus were studied. The results showed that the instrument detection limit and method detection limit of phosphorus were 0.028 and 0.084 mg·L-1, the relative standard deviation was between 0.6% and 3.9% in the accuracy test, recovery rates were between 102.3% and 103.0%. In addition, this method was compared with phosphor molybdenum blue spectrophotometry, and the results were basically consistent. This method is quick and easy with good precision and recovery, which is suitable for the analysis of actual samples.