Using the oxidative modification of low density lipoprotein(LDL) as a model and the contents of thiobabituric acid reactive substences,vitaminle E and fluorscent substances,the inhibitory effects of Shengmaisan on oxidative madification of LDL induced by Cu2+ and Fe2+ were studied.The results showed that Shengmaisan inhibited the oxidative modification of LDL significantly,and the extents of inbibition of oxidative modification of LDL induced by Cu2+ and Fe2+ were similar.The protective effect of Shengmaisan is mainly to scavenge lipid free radical.