Emodin (6-methyl-1,3,8-trihydroxyanthraquinone) is a natural anthraquinone derivative with potential pharmacological such as cytotoxic effects. The structure modification could be performed to determine the functional groups that have the role of substance activities. In this study, we modified one hydroxy group in the emodin structure to become dimethyl carbamoyl moiety. Emodin was reacted with dimethyl carbamoyl chloride and potassium carbonate to create 3-dimethyl carbamoyl emodin. The structure of the product was elucidated using mass spectrophotometer (MS), Fourier transform infrared (FTIR), proton and carbon nuclear magnetic resonance (H-NMR and C-NMR). These substances were tested for cytotoxicity against HepG2 cell lines using the MTT assay. According to the evaluation, 3-dimethyl carbamoyl emodin is less cytotoxic than emodin. As a result, the hydroxy group at the C3 position of emodin has been identified as a functional component that contributes to its cytotoxic effect.