Objective To observe the effect of Guanxinshutong（GXST）Capsule on myocardial microcir⁃ culation and prognosis in patients with Acute ST⁃segment Elevation Myocardial Infarction（STEMI）after Emergency percutaneous coronary intervention（PCI）. Methods A total of 210 patients with STEMI who underwent emergency PCI were randomly divided into two groups. One group was treated with conventional therapy（control group，n = 112）while the other with conventional therapy plus GXST Capsule（GXST group，n = 98）. Cardiac ultrasound and myocardial contrast echocardiography were performed on admission and after 1 ⁃ year follow ⁃ up respectively. LVEDV，LVEF and contrast score index（CSI）were recorded and compared. they were followed up to determine whether MACE occurred 1 year later. Results CSI on admission had no difference between the two groups but was significantly lower in GXST group after 1⁃y follow⁃up（P = 0.039）. MACE in GXST group（14.3%）was significantly lower than that in the control group（25.9%）（P = 0.041）. Multivariate logistic regression analysis demonstrated that the CSI after 1 ⁃ y follow up was an independent predictor for MACE（HR = 4.21，P = 0.040）. Conclusion GXST Capsule can improve myocardial microcirculation function in patients with STEMI after emergency PCI and it can also inhibit myocardial remodeling and reduce the occurrence of MACE. CSI level after 1⁃y follow⁃up is an inde⁃pendent risk factor for MACE.