Aim To investigate the apoptosis of vascular smooth muscle cells (VSMC) of rats induced by oxidized low density lipoprotein (ox LDL) and the mechanism of its action. Method The cell morphology, terminal deoxynucleotidy1 transferase mediated dUTP nick end labeling (TUNEL) assay, flow cytometry and Western blotting were performed for ox LDL inducing apoptosis of VSMC in rats. Results VSMC treated with ox LDL (200 mg/L) underwent the arrests of cell mitosis at metaphase, and the apoptosis index was as 10 times higher in VSMC treated with ox LDL as nLDL. The VSMC treated with ox LDL showed cell shrikage, condensation or fragmentation of chromosomes and apoptotic body. TUNEL assay showed brown and positive particles in apoptotic chromosomes and cytoplasma. The expression of P53 significantly increased, bcl 2 decreased in ox LDL treated cells. Conclusion Ox LDL induced apoptosis of VSMC, causing mitotic arrest of cells cycle, and promoting P53 and lowering bcl 2 gene expression. This indicated P53 and bcl 2 genes may play important role in VSMC’ apoptosis induced by ox LDL. 还原