[Abstract]Objective To make the childhood simple obesity animal model by adjusting the litter size of offspring and compare with the obesity model by high fat diet.Methods After 48 female KM mice farrowing, the litter size of half of them remain 14-16, the other adjust to 6 (3 male and 3 female).Pups were fed with basic diet and high fat at 4 or 9 week old and continued to the fifteen week.Weight, body length, waist circumference, weight of genital organ, fat weight including perirenal fat and genital organ fat were weighed and the ratio of body fat were calculated.Results ①There was significantly difference in the female or male body weight between BD1 and BD2 group feeding the basic diet for 15 weeks (P<0.05), and the body weight of BD2 were over 26.3%(female), 20%(male). The ratio of body fat of female in each group were higher than male’s under the same treatment methods.② No matter when we changed the diet or whether we adjusted the litter size or not, the body weight of newborn rats feeding HFD, both male and female, were higher than BD1 group (all P<0.05).Female and male offspring rats body weight in HFD4 group had significant higher than BD2 group (all P<0.05).Conclusion Childhood simple obesity animal model could be successfully prepared by adjusting the litter size.They began to intake high fat diet at adult stage,who got childhood simple obesity,would make the body store more fat.