Aim The antioxidation effect of Na₂SeO₃ and ZnSO₄, on the oxidation of human low density lipoprotein(LDL) were investigated by rat's arterial smooth muscle cells(ASMC). Methods Oxidation of LDL was induced by rat's ASMC added 1 μmol/L Cu²⁺ . The extent of LDL modification was assessed by measuring the formation of thiobarbituric acid reactive substance(TBARS). Results Treatment of 10 μmol/L Na₂SeO₃ and ZnSO₄ inhibited ASMC proliferation by ox-LDL(P<0.01). Treatment of 10 μmol/L Na₂SeO₃ inhibited MDA production(P<0.01), but 10 μmol/L ZnSO₄ have no the effect. 50 mg/L LDL induced myoleperoxidase(MPO) activity, but 10 μmol/L Na₂SeO₃ can not inhitit the effect. Conclusion 10 μmol/L Na₂SeO₃ could protect LDL against rat's ASMC inducing oxidation modification in vitro, which might be contributed by its effect to tyrosyl radical generated by myoleperoxidase.