Objective：To investigate the inhibition effects of methylase inhibitor 5-aza-2-deoxycytidine on human keloid fibroblasts，and the effects of 5-aza-2-deoxycytidine on related cytokines of human keloid fibroblasts. Methods：Human keloid and surrounding normal skin samples were collected for primary cultured fibroblasts. Cells were divided into keloid fibroblast experimental group，normal skin fibroblast experimental group，keloid fibroblast control group and normal skin fibroblast control group. 5-aza-2-deoxycytidine was used to intervene the experimental groups. Expressions of TGF-β1mRNA and Smad7mRNA in each group were detected with RT-PCR. Effects of 5-Aza-2-deoxycytidine on the cell cycle and apoptosis of fibroblasts were analyzed with flow cytometry（FCM）. Results：Compared with those of normal skin fibroblast，expressions of TGF-β1mRNA was increased（P=0.001） but Smad7mRNA were decreased（P=0.001） in keloid fibroblast，meanwhile the proportion of cells in G0/G1 stage（P=0.035） and apoptosis cells were decreased（P=0.006）. Expressions of TGF-β1mRNA were decreased（P=0.003） and those of Smad7mRNA were elevated（P=0.000） in keloid fibroblasts intervened by 5-aza-2-deoxycytidine. FCM demonstrated that the proportions of cells in G0/G1 stage and apoptosis cells were increased（P=0.000，P=0.047） in keloid fibroblasts intervened by 5-aza-2-deoxycytidine. But changes in normal skin fi－broblast group were insignificant（P >0.05）. Conclusions：Methylaze inhibitors，5-aza-2-deoxycytidine may inhibit the proliferation and promote the apoptosis of keloid fibroblast as well as influence expressions of its related cytokines，however，the effects on normal skin fibroblasts are insignificant. Pathogenesis of keloid may relate with the methylation of certain genes. 5-aza-2-deoxycytidine may be a new choice in the treatment of pathological scar.