OBJECTIVE： To study the preventive and therapeutic effects of Xinmaitong tablets on model rats with atherosclerosis （AS） and corresponding mechanism. METHODS： 48 rats were randomized into normal group， model group， positive group （simvastatin tablets， 2 mg/kg） and the groups of high， medium and low-dose （500， 250， 125 mg/kg） Xingmaitong tablets， with 8 rats in each group. The rats in all groups except for the normal group were fed high fat diets and given vitamin D3 ip for the establishment of AS model. Meanwhile， the rats in the drug administration groups were given corresponding drugs ig， while those in the normal group and the model group were given normal saline ig， once a day， for 10 consecutive weeks. The levels of cholesterol （TC）， triacylglycerol （TG）， nitric oxide （NO） and endothelin 1 （ET-1） in serum were determined. The pathological change of the aorta tissue was observed under the light microscope， and the size of the aortic atherosclerotic plaque and intima thickness were measured. RESULTS： Compared to the normal group， the rats in the model group had significantly higher levels of TC， TG and ET-1 in serum， a markedly larger aortic atherosclerotic plaque， remarkably thicker intima and much lower level of NO （P＜0.01）； and obvious aortic atherosclerotic plaque formation was found. Compared to the model group， the above-mentioned indexes of the rats in all drug groups all improved obviously （P＜0.05 or P＜0.01）， except that the decrease in TC in serum of the rats in the group of low-dose Xinmaitong tablets was not significant， which were positively correlated with dose； and the aortic lesion in drug groups was found to be improved. CONCLUSIONS： Xinmaitong tablets have certain preventive and therapeutic effect on the model rats with AS by a mechanism which may be related to the reduction in lipid deposition and the size of an atherosclerotic plaque， the improvement in NO/ET balance and the alleviation of an endothelial injury.