The root of Angelica sinensis (RAS) is a traditional Chinese medicine used for preventing and treating various diseases. In this study, we assessed RAS supplementation effects on body weight and the FTO gene expression and methylation status in a high-fat-diet (HFD) induced obese mouse model. Female obese mice were divided into groups according to RAS dosage in diet as follows: normal diet, HFD diet (HC), HFD with low-dosage RAS (DL), HFD with medium-dosage RAS (DM), and HFD with high-dosage RAS (DH). After RAS supplementation for 4 weeks, body weight suppression and FTO expression in DH mice were significantly higher than in HC mice, whereas no significant change in FTO expression was detected between DM and DL mice or in their offspring. Bisulfite sequencing PCR (BSP) revealed that the CpG island in the FTO promoter was hypermethylated up to 95.44% in the HC group, 91.67% in the DH group, and 90.00% in the normal diet group. Histological examination showed that adipocytes in the DH group were smaller than those in the HC group, indicating a potential role of RAS in obesity. This study indicated that RAS could ameliorate obesity induced by HFD and that the molecular mechanism might be associated with the expression of the FTO gene.