Abstract: Ammonium pyrrolidine dithiocarboxylic acid (APDC) was used to subside and gather trace iron of high purity lutetium oxide, and the precipitate of which was dissolved in methyl isobutyl ketone (MIBK). After separation and enrichment, the solution was determined by GF-AAS. When the acidity of liquid is 0.4 mol/L, the volume of 2 % APDC is 2 mL, settling time is 15 min, ashing temperature is 1 100 ℃, and atomization temperature is 2 300 ℃, determination result of Fe is the optimum. Matrix elements such as Pb, Ni, Cr, Co and Cu have no interference on the determination of Fe. This method is comparatively accurate and precise with relative standard deviation of 4.5 %, and the recovery rate within the range of 94.0 %~108.0 %.