Objective To explore the effects of DNMT3b on the expression and methylation sta-tus of the promoter region of DLC-1 in human hepatocellular carcinoma cell line. Methods The SMMC-7721 cell line was divided into 2 groups. The cell line in the experimental group was transfect-ed with DNMT3b siRNA, while that in the control group was transfected with control siRNA. West-ern blot was used to detect the expression of DNMT3b and DLC-1 and MSP was employed to examine the methylation status of the promoter region of DLC-1. Results The expression of DNMT3b was significantly higher in the experimental group than in the control group, while the expression of DLC-1 was just opposite. There was no significant difference in the methylation status of the promoter re-gion of DLC-1 between the 2 groups and both were methylated. Conelnsion The inhibition of expression of DNMT3b by siRNA method can enhance the expression level of DLC-1, and the methylation status of the promoter region of DLC-1 does not change at the same time. When affecting the expression of DLC-1, DN-MT3b might not play the role of methyhransferase, but can act as a transcriptional regulatory factor.