As a pre-digestion method of breast milk microwave-digestion was adopted in this method, and the contents of calcium and phosphorus were determined by ICP-MS at the same time. By optimizing conditions of digestion and ICP-MS, appropriate internal elements and the isotope mass number and EPA200.8 interference calibration equation were chosen. The accuracy and reliability of method were verified through the recovery and milk powder analysis of national standard substances (GBW10017). Determination results are in the permissible range. The relative deviation(RSD)is less than 2.40%, while the recovery is between 102.8％ and 104.0％. ICP-MS method has wide dynamic range, and doesn’t need to dilute samples. It is suitable for lots of samples and multi-element analyzed at the same time, and making up default of different method and different element determined respectively in national standard. It is a determination method for calcium and phosphorus supply of breast milk.