The skin tissues of 15 patients with psoriasis vulgaris （psoriasis group） and 15 healthy controls （control group） were collected. Real-time fluorescence quantitative PCR（RT-qPCR） method was used to detect the expression levels of DNMT3a mRNA in skin tissue of the subjects in two groups. The Si-DNMT3a silenced by DNMT3a was transfected into the HaCaT cells by siRNA transfection technology. RT-qPCR and Western blotting methods were used to detect the transfection efficiency of si-DNMT3a. The HaCaT cells were induced by M5 method and the psoriasis like cell model was established. The cells were divided into control group， si-DNMT3a group， si-NC group， and HaCaT group. The proliferation rates of the cells in various groups were detected by CCK-8 method， the percentages of the cells at different cell cycles in various groups were detected by flow cytometry， and the apoptotic rates of the cells in various groups were detected by Annexin Ⅴ-FITC test. MSP test was used to detect the methylation levels of LATS1 gene promoter in skin tissue of the subjects in psoriasis group and control group. The expression levels of large tumor suppressor gene 1（LATS1）， Yes associated protein（YAP1）， cyclin D1， CDK6， and cleaved caspase-3 proteins in the HaCaT cells in various groups were detected by Western blotting method.

Compared with control group， the expression level of DNMT3a mRNA in skin tissue of the patients in psoriasis group was significantly increased （P<0.01）. Compared with HaCaT group，the expression levels of DNMT3a mRNA and protein in the HaCaT cells in si-NC group were decreased （P<0.05）. Compared with HaCaT group， the proliferation rates of the HaCaT cells and the percentages of cells at S phase in control group， si -NC group，and si- DNMT3a group were increased （P<0.05）， and the percentages of cells at G₁ phase and the apoptotic rates were significantly decreased （P<0.05）；compared with control group and si-NC group， the proliferation rates of the HaCaT cells and the percentage of cells at S phase in si-DNMT3a group were significantly decreased（P<0.05），and the apoptotic rate and the percentage of cells at G₁ phase were increased （P<0.05）. The MSP results showed that the methylation level of LATS1 promoter in skin tissue of the patients in psoriasis group was higher than that in control group （P<0.01）. The Western blotting results showed that compared with HaCaT group， the expression levels of YAP1， Cyclin D1， and CDK6 proteins in the HaCaT cells in control group， si-NC group，and si-DNMT3a groups were increased （P<0.05）， while the expression levels of LATS1 and cleaved caspase-3 proteins were decreased （P<0.05）； compared with control group and si-NC group， the expression levels of YAP1， cyclin D1， and CDK6 proteins in the HaCaT cells in si- DNMT3a group were decreased （P<0.05）， and the expression levels of LATS1 and cleaved caspase-3 proteins were increased （P<0.05）.

Silencing the DNMT3a expression may down regulate the expression of YAP1 by reducing the methylation level of LATS1， so as to inhibit the progression of psoriasis like HaCaT cell cycle and cell proliferation and induce the apoptosis.