Aim To evaluate the incidence of intramyocardial hemorrhage (IMH) after percutaneous coronary intervention surgery for acute ST-segment elevation myocardial infarction (STEMI) in the Chinese population, and to explore the relevant predictive factors for the IMH formation and provide individualized diagnosis and treatment measures for patients with STEMI . Methods The observation cohort study of our center was conducted in patients with STEMI undergoing successful myocardial reperfusion. The cardiac magnetic resonance (CMR) examination was (5.71±2.46) days after emergency percutaneous coronary intervention (PCI). T2 weighting was used to observe IMH in cardiac tissue, and the basic data, laboratory examination, echocardiography (UCG) and CMR parameters of IMH and non-intramyocardial hemorrhage (non-IMH) patients were compared. Logistic regression analysis was used to screen out risk factors related to intramyocardial hemorrhage. Results 44 (48.9%) of the 90 patients enrolled had IMH. Compared with the non-IMH group, IMH patients had a higher incidence of obsolete cerebral infarction and pre-hospital oral diuretics. Faster heart rate, higher C-reactive protein (CRP), relatively lower myocardial staining score (all P＜0.05) were also observed in IMH group. Compared with non-IMH group, UCG showed that left ventricular end diastolic diameter (LVEDd) increased in IMH group, CMR showed that left ventricular end-diastolic volume (LVEDV), total myocardial infarction size (IS)/the volume of left ventricular (LV), microvascular occlusion (MVO) area/the volume of LV were all increased (all P＜0.05). Compared with non-IMH group, the incidence of IMH was significantly related to the decrease of left ventricular ejection fraction (LVEF), global radial strain (GRS),global circumferential strain (GCS) and global longitudinal strain (GLS) (all P＜0.05). In IMH group, the left anterior descending artery (LAD) lesions were more frequent, and the myocardial infarction sites were more frequent in the anterior wall, interventricular septum and apex of the heart, meanwhile pericardial effusion and aneurysm were more likely to occur (both P＜0.05). Multivariate Logistic regression analysis suggested that IMH was independently associated with anterior myocardial infarction (OR:5.9,5%CI:1.28～27.95, P＜0.05), decreased percentage of peak GLS measured by CMR (OR:1.7,5%CI:1.21～2.03, P＜0.05) and high low density lipoprotein cholesterol (LDLC) (OR:4.2,5% CI:1.45～15.38, P＜0.05). Conclusion Among STEMI patients treated with myocardial reperfusion, the IMH has a strong correlation with anterior wall myocardial infarction, GLS reduction, and LDLC increase, which can be used to identify the potential risk factors for IMH in STEMI patients. IMH is associated with more severe infarction and worse left ventricular function, and is more likely to be associated with ventricular aneurysm and pericardial effusion.