Abstract: Objective To explore the relationship between hepatitis B virus (HBV)X pro-tein and inhibited expression of CCL13 cells Period 1.Methods The pcDNA3.1-HBx plasmid was transfected into CCL13 cells by Lipofectamine in vitro.Period1 expression and its promoter methylation level in CCL13 and CCL13-HBx were detected by treatments of reverse transcription PCR,western blot and methylation-specific PCR.Results The human liver cell lines CCL13-HBx contained stable HBx gene expression.Compared to CCL13,methylation level of period1 promoter increased in CCL13-HBx,and expression level of its mRNA and protein decreased.Conclusion Hepatitis B virus X pro-tein can decrease period1 expression in CCL13 by up-regulating its promoter methylation level.