Objective： To explore the value of three-dimensional speckle tracking technique（ 3 D-STI）in evaluating left ventricular systolic function in patients with ST segment elevation acute myocardial infarction（ AMI） after PCI. Methods： 70 patients with STEMI and 70 cases healthy people in Zhongshan Torch Development Zone Hospital and The Second Affiliated Hospital of Guangdong Pharmaceutical University from August2015 to August 2016 were selected into the clinical data. All patients were followed by conventional ultrasound and 3 D-STI at 12 months. Two sets of measurement result were recorded. Results： The left ventricular end systolic volume,left ventricular end diastolic volume and left ventricular end diastolic diameter in the case group were higher than those in the control group（ F = 75. 87,57. 30,231. 84,P〈0. 01）. The left ventricular ejection fraction in the case group was lower than that in the control group（ F = 51. 40,P〈0. 01）. The overall longitudinal strain,overall circumferential strain,overall radial strain and left ventricular ejection fraction in the case group were lower than those in the control group（ F = 316. 01,202. 31,68. 21,203. 58,P〈0. 01）.Conclusion： After 12 months of PCI,the left ventricular systolic function in patients with ST segment elevation AMI is still low,who need to continue to follow up. 3 D-STI can be used to estimate the left ventricular systolic function.