Abstract: Sample of flame-retardant fiber was digested with a mixture of H2SO4,HNO3 and H2O2 in a closed PTFE vessel,heated at 230 ℃ and under the pressure of 4.0 MPa by using the microwave sample digestor.The solution obtained was used for ICP-AES determination of phoshporus.Among the 3 spectral lines tested (i.e.,213.618 nm,214.914 nm and 253.561 nm),serious interferences due to titanium(Ⅳ) and traces of Cu(Ⅱ) were encountered when the spectral lines of 253.561 nm and 213.618 nm were chosen as the analytical lines,and the interferences were effectively eliminated by choosing the spectral line of 214.914 nm as analytical line.It was also shown that under the optimum condition,matrix matching was not necessary in the preparation of standard curve of phosphorus.Detection limit (3σ) of the method was found to be 36.0 μg·L-1.Tests for recovery and precision were made,giving results of recovery in the range from 83.8% to 107.8% and RSD′s (n=10) less than 2%.