Abstract: The rare earth impurities of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y in lanthanum-iron alloy were determined by inductively coupled plasma optical emission spectrometry(ICP-OES). The effect of matrix on the determination of lanthanum-iron alloy in nitric acid medium was corrected by approximate matrix matching method, and the spectrum was determined by standard curve method. The analytic lines were selected by profile scanning method to screen the optimum lines with flat background, high signal to background ratio and low matrix interference from several pre-selected lines. The standard solution was prepared by matrix matching method, according to product standard XB/T 407—2020 index by iron (85%) and lanthanum (15%) and 6 series of standard solutions for curve drawing.The method obtained is suitable to determine Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y contents in the range of 0.005%~0.25% and the RSD is between 0.74% and 2.58% (n=11). Standard addition method was applied for accuracy test and the recovery rate is in the range of 91.75%~107.75%.