Objective To analyze the prognostic value of four-dimensional ultrasound automatic quantitative analysis combined with heart rate variability (HRV) detected by electrocardiography in patients with acute myocardial infarction (AMI). Methods A total of 83 patients with AMI admitted to the hospital from March 2020 to March 2022 were selected. All patients underwent four-dimensional ultrasound examination and electrocardiography. They were divided into the major adverse cardiovascular events (MACE) group and the non-MACE group according to the prognosis. Ultrasound parameters and HRV in the two groups were comparatively analyzed, and their correlation with the incidence of MACE was analyzed. The prognostic value of the combination of the two imaging methods was evaluated. Results Left atrial emptying volume (LAEV), left atrial passive ejection fraction (LAPEF), left atrial active ejection fraction (LAAEF), left ventricular ejection fraction (LVEF), and global radial peak strain (GRPS) ,etc in the MACE group were lower than those in the non-MACE group. The maximum left atrial volume index (LAVImax) was higher than that in the non-MACE group (P<0.05). The standard deviation of normal RR intervals (SDNN), the standard deviation of the averages of R-R intervals (SDANN), the root mean square of successive RR interval differences (RMSSD), low frequency (LF)/high frequency (HF), and the percentage of RR intervals with >50ms variation (PNN50) in the MACE group were lower than those in the non-MACE group (P<0.05). LAEV, LAPEF, LVEF, GAPS and SDNN were negatively correlated with the incidence of MACE, while LAVImax was positively correlated with the incidence of MACE (P<0.05). The area under the curve, sensitivity and specificity of LAEV, LAPEF, LVEF, LAVImax, GAPS, and SDNN in combination to predict the prognosis of patients with AMI were 0.841, 0.81 and 0.76, all of which were higher than single prediction. Conclusion Four-dimensional ultrasound automatic quantitative analysis combined with HRV detected by electrocardiography is of high prognostic value in patients with AMI.