Aim To observe the methylation levels of B1 and Alu sequences in different tissues of ApoE^-/- mice and human vascular smooth muscle cells induced by homocysteine （Hcy）, so as to further clarify the molecular mechanisms of Hcy-induced atherosclerosis （As）. Methods The hyperhomocysteinemia ApoE^-/- mice model were replicated, and the heart tissues, aortas and white blood cells were taken from mice after fed for 14 weeks. 50, 100, 200, 500 μmol/L Hcy were added into the primary cultured human umbilical vein smooth muscle cells for 72 h. The genomic DNA were extracted from the heart tissues, aortas, white blood cells and vascular smooth muscle cells. Then the methylation status of B1 and Alu repetitive sequences were examined by nMS-PCR. Results The methylation levels of B1 repetitive sequences were significantly decreased in the heart tissues, aortas and white blood cells of ApoE^-/- mice fed with high methionine diet. Compared with the control group, there were significant differences （P<0.05 and P<0.01）. The m-