Abstract: Acute oral toxicity test of banana powder was studied. And according to the testing assessment of weight-losing function of health food published by Ministry of Health, the effect of banana powder on weight losing of SPF grade SD male rats with nutritional obesity was studied. Through continuous observation for 14d after the administration of banana powder, the activity of mice was normal with bright fur, no abnormal secretions, normal weight gain and no mouse dead. Visual inspection after gross anatomy of all surviving mice revealed no changes in organ volume, color and texture. The treatment of banana powder could significantly decrease body weight, fat tissue weight around the testicle and kidney, body fat percentage and Lee’s index of the rats (p<0.05) . Moreover, the serum levels of total cholesterol (TC) , total triglyceride (TG) and low density lipoprotein cholesterol (LDL-C) were markedly decreased by banana powder while high density lipoprotein cholesterol (HDL-C) was significantly increased (p<0.05) . Altogether, the result indicated that banana powder had an effective function of weight losing.