Abstract：The purpose of this study is to observe the effect of Simiaoyong'an Decoction (SYD) on Atherosclerosis (AS) vulnerable plaque. 40 Japanese white rabbits were randomly assigned to two groups: 10 in the normal control group, and 30 in the experimental group to be established as the AS model by high fatty diet feeding, combined with immune injury at the 2nd week and femoral arterial balloon tearing at the 4th week. At the 8th week, 30 rabbits in the experimental group were randomly assigned to four groups: each 10 in the model group, the SYD group and the simvastatin group. The medication of SYD and simvastatin were given in the whole 16-week course. Levels of monocyte chemotactic protein-1 (MCP-1), and intercellular adhesion molecule (ICAM-1) and CRP were measured at the 8th, 16th and 24th weekend in experiment. The tumor necrosis factor alpha (TNF-α) and the nuclear factor-kappa B (NF-κB), HSP60 expression in aortic wall were measured at the end of experiment. The results show that compared with the model group, the levels of MCP-1, ICAM-1 are lower in the two treated groups at all time points after treatment (P<0.01 or P<0.05). TNF-α, NF-κB and HSP60 expression in aortic wall are lower after treatment (P<0.01 or P<0.05). In overall, it is demonstrated that SYD could stabilize atherosclerosis vulnerable plaque by suppressing the inflammation reaction.