Objectives : This study is to investigate the effects and mechanisms of Imyo-san (IMS) on the obese mice model induced by high-fat diet. Methods : Antioxidative capacity was measured by in vitro method. C57BL/6 mice were randomly assigned into 5 groups (n=7). Normal group was fed general diet (Normal). The other 4 groups were fed high fat diet (HFD) with water (Control), with Garcinia gummi-gutta (GG, Garcinia gummi-gutta 200 ㎎/㎏), with low-dose IMS (IMSL, Imyo-san 0.54 g/㎏) and with high-dose IMS (IMSH, Imyo-san 1.08 g/㎏). Results : IMS showed high radical scavenging activity. After 6 week experiment, body weight, food intake, food efficiency ratio(FER), epididymal fat and liver weight, triglyceride(TG), total cholesterol (TC), high density lipoprotein(HDL) cholesterol, low density lipoprotein(LDL) cholesterol, very low density lipoprotein(VLDL) cholesterol, SREBP-1, p-ACC, FAS, SCD-1, SREBP-2, HMGCR, p-LKBI, p-AMPK, PPARα, PGC-1α, UCP-2, CPT-1A, and histology of liver and epididymal fat were measured and analysed. Body weight gain, FER, liver and epididymal fat weight of IMS groups were significantly decreased. There were significant improvements in blood lipids with less TG, TC, LDL-cholesterol, VLDL-cholesterol and more HDL-cholesterol. Proteins associated with lipid synthesis (SREBP-1, p-ACC, FAS, SCD-1) and cholesterol (SREBP-2, HMGCR) was improved. Factors regulating lipid synthesis and lipid catabolism (p-LKBI, p-AMPK, PPARα, PGC-1α, UCP-2, CPT-1A) were increased. In histological examinations, IMS group had smaller fat droplets than control group. All results increased depending on concentration. Conclusions : It can be suggested that IMS has anti-obesity effects with improving lipid metabolism.