Abstract: Objective To study the effect of chitosan on fat rat bodyweight,body fat content,yorgan index,concentration of serum leptin,lipids and their relationship.Methods Young male rats were induced into fat model and then divided into eight groups.The rats were given base diet or high fat diet containing three doses of chitosan for 7wk.By the end of week 7,the rats were sacrificed and their blood samples were taken,the concocentration of serum leptin and lipids were determined.Results High dose of chitosan produced a significant decrease in fat rat body weight and body fat content.Compared with control group(P<0.05),all chitosan-containing diets produced a significant decrease in serum triglyceride(T G),total cholesterol(TC)and leptin,but the level of high-density lipoprotein-cholesterol(HDL-C)was increased.Conclusion Based on analysis on the change of body weight and serum leptin level,it was referred that chitosan could improve leptin2resising,which could be in part responsible for reducing body weight of fat rats.