Abstract: The method of determining the trace free copper in feed additives by single-sweep polarography in the system H2SO4-EDTA- KNO3-gelatin was put forward. The free copper in sample was extracted by nitrate extraction. The polarographic peak potential of copper was -0.2 V （relative to saturated calomel electrode）. In the range of 0.1-100 μg/mL, the conen, of copper showed good linear relationship with peak current. The detection limit of copper was 0.04 μg/mL, its RSD was 3.3 % and its recovery of standard addition was 97 %.This method was simple and convenient. The determination by this method was fast and precise, so it could be used in the practical determination of samples.