Objective：To investigate the protective effects of Xuemaitong capsule on experimental rats with acute myocardial infarction （AMI） and to explore its mechanism． Methods：Wistar rats were randomized into 5 groups：model group，sham operation group，three different dose groups of Xuemaitong capsule preconditioning. Rats in model group were treated by continuous intragastric administra－tion for 14 d. After 14 d，myocardial infarction of all groups was established by ligation of coronary artery except sham operation group. Electrocardiogram was recorded before ligation and at １5，30，60，90，120 min and 24 h after ligation. Pathological changes and infarcted area of cardiac tissues were checked by HE staining combined with nitroblue tetrazolium staining.Immunohistochemical staining，RT-PCR and image analysis were used to measure expressions of matrix metalloproteinase-9（MMP-9） and nuclear factor-κB（NF-κB） in the myocardial infarction. Results：J points in electrocardiogram in Xuemaitong capsule treated groups were elevated at differ－ent degrees compared with that in model group. Meanwhile，pathological alteration of myocardial infarction in Xuemaitong capsule treated groups was ameliorated compared with that in model group. Immunohistochemical staining indicated that protein and mRNA expressions of MMP-9 and NF-κB were decreased in high dose group and middle dose group（P<0.05 or P<0.01）. Conclusions：Xue－maitong capsule has protective effects on AMI of rats induced by ligation of coronary artery，decreased protein and mRNA expressions of MMP-9 and NF-κB may be one of the mechanisms.