Abstract: 210 one-day-old Tianfu meet ducklings were divided into three groups, and fed on diets as follow: control (Cu 12.16 mg/kg)， copper toxic I (Cu 850 mg/kg) and copper toxic Ⅱ ( Cu 1 050 mg/kg) for studying effects of copper toxicity on organs and serum enzyme activities in duckling by the methods of experimental pathology. At pathological level, there were similar lesions in both two copper toxic groups compared with control group. At necropsy, the cuticle of gizzard was thickened. The digestive tract was full of the black-brown, red-brown or light-green substance and intestinal mucosa was swelled. Lymphoid organs were smaller in both copper toxic groups than that in control group. At histopathological level, the hepatocytes, epithelial cells of renal tubule and cardiac muscle cells mainly showed granular and vacuolar degeneration. The epithelial cells of intestinal mucosa were degenerated and necrotic. The intestinal villi were broken. Lymphocytes of lymphoid organs were depleted, degenerated and necrotic.At ultrastructural level, the mitochondria of hepatocytes were swelled, and its crista were broken or / and disappeared. The deposited substance with high electron density appeared in the cytoplasma and nucleus of hepatocyte. The serum caeruloplasmin activity was much lower, and serum glutamicpyruvic transminase and glutamic-oxaloacetic transminase activities were much higher in copper toxic groups than that in control group. The above mentioned results demonstrated that the target organs impaired by copper toxicity were liver, kidney, heart, gastrointestines and lymphoid organs. The death of affected duckling due to the injury, disfunction of organs.