Abstract: A method for the determination of phosphorus content in coal samples with Microwave Digestion was established by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The samples of lignitic coal, bituminous coal and anthracite coal were completely dissolved in HNO₃-H₂SO₄-HF mixed acids at a temperature greater than 180℃ by high-pressure-airproof microwave digestion. The phosphorus was measured by ICP-AES using the 178.283 nm spectral line for analysis. The matrix interferences and spectral interferences were avoided by background correction. Si, Fe, Ca, Al and Mg have no outstanding effect on the measurement phosphorous. The linear range for phosphorus was 0-10 mg/L, and the detection limit was 0.09 mg/L. This method, when applied to the determination of phosphorus content in coal yields a relative standard deviation (RSD) of 1.89%-5.21% and recovery factors of 94.5%-101.2%. The results obtained using this method are in good agreement with the values of certified reference materials.