Aim To study the expression of P21 gene in vascu-lar smooth muscle cells(VSMC)induced by introduc-tion of wild-type P53 gene and explore the mechanism of regulation for cell cycle progression by wild-type P53 gene.Methods A P53 gene recombinant adenovirus vec-tor,AdCMVP53.was transfected into the cultured SMC derived from human umbilical artery.The gene expression of P21 was quantified by reverse transcrip-tion-polymerase chain reaction(RT-PCR).The con-tent of P21 was detected by immunochemical staining.Flow cytometry was used for cell cycle analysis.Results The level of P21 mRNA and protein was increased in VSMC transfected with AdCMVP53.Overexpression of wild-type P53 could arrest the SMC at G0/G1 phase of the cell cycle.Conclusion Wild-type P53 gene could induce the expression of P21 gene,leading to repression of cell cycle progression.