Abstract: Steel sample was dissolved in mixed acid of HCl-HNO3 (3+1), and content of phosphorus in the sample solution was determined by FAAS, based on the fact that in an appropriate acetylene-air flame, diatomic molecule of PO is formed, and its concentration determined at the selected wavelength of 327.04 nm. Linear relationship between values of absorbance and mass concentration of phosphorus was obtained within 1.0 g·L-1, with detection limit (3s) of 0.001 g·L-1. The proposed method was applied to the analysis of 2 certified reference materials of steel (YSBC 20310-2002, GBW 01312), giving results in consistency with the certified values, and values of RSD′s (n=5) found were less than 4%.