The sample was dissolved in hydrochloric acid and nitric acid . hydrofluoric acid and perchloric acid were added to sample solution.The sample solution was heated and evaporated until dry to remove silicon tetrafluoride and hydrofluoric acid.After soluble salt was dissolved in dilute hydrochloric acid, copper in the solution was determined by flame atomic absorption spectrometry.The effect of dissolving sample with different proportion of mixed acids and the interference of different medium, acidity and coexistent elements were examined. The result indicated the sample could be completely dissolved in hydrochloric acid + nitric acid+ hydrofluoric acid + perchloric acid. Hydrochloric acid with the volume fraction of less than 2.5% did not affect the determination of copper. In 100 mL of solution, 40 mg of nickel, 1 mg of cobalt and 10 mg of chromium did not affect the determination of 0.02 mg of copper. 200 mg of iron did not also affect the determination of more than 0.02 mg of copper. However, different amounts of iron affected the determination of 0.01-0.02 mg of copper. Therefore, interference for determining low content of copper may be eliminated by adding iron in blank solution. The detection limit of copper was 0.011 μg/mL and the limit of quantitation was 0.038 μg/mL. The method was used for real sample analysis of nickel substrate. The RSD of the determination result (n=11) was within the range of 1.7%-2.0% and the recovery was between 98%-108%.