Abstract: Objective To study the effect of medium chain triglycerides（MCT） on brown adipose tissue（BAT） in C57BL/6J mice. Methods Thirty male C57BL/6J mice at the age 4-5 weeks,enrolled in this study,were randomly divided into MCT group,LCT group and control group（10 in each group）.Animals in the first two groups were fed with high fat diet containing MCT or LCT,and those in control group were fed with standard chow for 15 weeks.Body weight,subscapular brown fat mass,diet consumption,and uncoupled protein-1（UCP1） expression in BAT of different groups were observed. Results After 15 weeks,the body weight and body fat mass were significantly lower in MCT group than in LCT group（P＜0.05）.No significant difference was noted in diet consumption between MCT and LCT groups（P＞0.05）.The brown fat mass and UCP1 expression were significantly higher in MCT group than in LCT group（P＜0.05）. Conclusion MCT can inhibit the increase of body mass and accumulation of body fat due to high fat diet by increasing brown fat mass,UCP1 expression and heat production in brown fat tissue.