Objective To explore the application of quantitative T2 mapping for assessing the myocardial edema after myocardial infarction (MI) and analyze the correlation between T2 value, area of myocardial edema, and the peak value of biochemical index creatine kinase (CK). Methods Thirty patients with MI who underwent reperfusion therapy were retrospectively analyzed. Patients received cardiac magnetic resonance imaging (CMR) within 2-7 d after percutaneous coronary intervention (PCI). T2 values of edema region and distal normal myocardium and the area of edema were calculated and documented after images were collected. T2 values of edema region and distal normal myocardium were compared. The correlation of T2 values and the area of edema calculated via T2 mapping with serum CK was analyzed. Results ①T2 value [(59.18 ± 4.23)ms] of edema region was significantly higher than that of distal normal myocardium [(43.35 ± 2.11) ms](P=0.013). ②The area of edema region calculated via T2 mapping was positively correlated to the peak value of serum CK (r=0.82, P=0.000). ③T2 value of edema region was not correlated to the peak value of serum CK (r=0.475, P=0.054). Conclusion Quantitative T2 mapping is valuable for the assessment of myocardial edema in acute MI. The area of myocardial edema may be more important for the assessment of myocardial injury after acute MI.