Lead, Iron and Copper in antimony oxide were determined by FAAS. The method of dealing with the antimony oxide sample and the best determination conditions were studied by IF. Influences of acidity and elements interference were discussed. The rates of recovery of the three elements were from 95.4 % to 112.1 %, and the relative standard deviation (RSD) was less than 5.8%, The results were entirely satisfactory for antimony oxide.