Objective To observe the influence of emergency PCI in different time windows to cardiac scar and cardiac function after myocardial infarction. Methods One hundred and twenty-seven patients with acute myocardial infarction, who were treated in different time windows by emergency PCI, were enrolled into this study. The cases were divided into two groups according to the time when they took PCI after onset;group 3 hPCI included 66 patients had PCI at 3 h after onset and group 6 hPCI included 61 patients had PCI at 6 h. At 4th, 8th and 12th weeks, the fragmented QRS (fQRS) were observed by twelve synchronization cardiogram; ventricle wall movement strain rate were determined by cardiac speckle tracking imaging;left ventricular ejection fraction (LVEF)were measured by cardiac ultrasound to evaluate cardiac events and cardiac function after myocardial infarction. Results At 4th,8th and 12th weeks,the fQRS positive leads were significantly more in 6 hPCI group than 3 hPCI group ( P ＜ 0. 05 respectively ) . The ventricle wall movements strain rate and LVEF improved significantly in 3 hPCI group compared with 6 hPCI group (P ＜ 0. 05 ). Conclusions The earlier emergency PCI treatment was applied and the earlier the"criminal"blood vessels were opened ,the more ischemic myocardial cells were restored. Combination use of fQRS、 STI and LVEF examination could improve the diagnosis of cardiac scar formation and direct protective therapy.