Objectives This study was designed to evaluate the effects of Ephedra Sinica and Fibrosum Gypsum extract on obesity by using 3T3-L1 cells and high fat diet rats. Methods In vitro, Ephedra Sinica and Fibrosum Gypsum extract (50, 100, 200, $500{\mu}g/ml$) were added in 3T3-L1 cells. Cytotoxicity was measured by MTT assasy. Adipocyte differentiation was measured by Oil Red O staining, GPDH activity and $C/EBP{\alpha}$ protein expression. In vivo, Sprague-Dawley rats were divided into 5 groups : Normal diet group (Normal group), taken high fat diet and no treatment group (Control group), taken high fat diet and orally administered Ephedra Sinica and Fibrosum Gypsum extract daily (Group I: 50 mg/kg, Group II: 100 mg/kg, Group III : 200 mg/kg, oral). For 6 weeks of administration, body weight and the amount of food intake were measured once a week. After administration, blood analysis (AST, ALT, T-Bilirubin, BUN, RBC, Hb, HCT), serum lipid level (triglyceride, Total cholesterol, HDL, LDL), serum leptin level, epididymal adipose tissue weight and histological finding of liver were estimated. Results In vitro, The cytotoxicity was not significant. 3T3-L1 cell's differentiation was significantly decreased in Oil Red O staining, GPDH activity and $C/EBP{\alpha}$ protein expression. In vivo, Body weight and the amount of food intake, AST, ALT, Total cholesterol, TG, LDL, serum leptin, epididymal adipose tissue weight showed significant decrease in group I, group II and group III. There were no significant difference in T-bilirubin, BUN, RBC, Hb and HCT between all groups. HDL showed significant increase in group I, group II and group III. In histological finding of liver tissue, there were decreased adiposity and cytopathic effect in group I, group II and group III. Conclusions It is suggested that Ephedra Sinica and Fibrosum Gypsum extract can be used in the treatment of obesity.