Abstract: Based on the method of toxicology, mice were administered with different dosage of olaquindox by intragastric administration in order to investigate the effect of olaquindox on function of liver and kidney. The results were as follows: With the increase of olaquindox dosage, both the activity of GOT, GPT and the content of BUN, Cre in blood stepped up, the activity of CHE stepped up at first, and then stepped down, the content of TP and ALB stepped down obviously in serum. These results indicated that there was a decrease in anabolism of protein, and increase in catabolism, which resulted in a decrease in growth rates. At autopsia, the livers displayed swelling, blood stasis, and become breakable. Both denaturation and necrosis of liver cell were observed in 1/10 LD50 and 1/5 LD50 groups. The swelling, denaturation and desquamation was also observed in epithelia of nephridial tubule, at the same time, the glomerular capsule become incommodious. By electron microscope, plasmarrhexis, decrease of organelle, impairment of mitochondria were observed in partial liver cells in 1/5 LD50 group. Plasmarrhexis occurred in epithelia of proximal convoluted tubule, and impairment, vacuole appeared in mitochondrial cristae, while, there was some part fusion in Sertoli cells of glomeruli. These results confirmed the organic impairment of olaquindox on liver and kidney in mouse.