Abstracts: Objective To explore the chronic toxicity and carcinogenicity of pesticide pyraflufen-ethyl in rats. Methods According to National Standards of “Toxicological Methods of Pesticides for Registration” (GB15670-1995 of PRC), chronic toxicity tests and carcinogenicity tests were conducted. These samples were fixed in 10% neutral formalin firstly. Then the samples were embedded in paraffin after dehydration process. Afterward, the samples were sectioned and stained by hematoxylin-eosin(HE) staining. Finally, the sections were cemented by gum and observed in light microscope. Results Chronic toxicity tests revealed that the degeneration ratio of renal tubular epithelial cells in high dosage group was significantly increased comparing to control group (p≤0.01). Furthermore, the middle dosage group results showed there was a similar increasing in the proportion of tubulointerstitial nephritis (p≤0.05), however, there were no evident renal pathology differences between low dosage group and control group. In addition, other pathological changes in any dosage group were not remarkably different from control groups (p＞0.05). Statistical incidence variance of tumor, multiple primary neoplasms and tumor latency in different groups were not observed in carcinogenicity tests. Conclusion We found that the main target organ was kidney and sexual differences existed in chronic toxicity, in addition, the tumorigenesis of rats would not be elevated by Pyraflufen-ethyl.