Objective: This study analyzed three-dimensional echocardiography (3DE) combined with the triglyceride–glucose (TYG) index to evaluate the long-term prognosis of patients after percutaneous coronary intervention (PCI). Methods: The clinical data of 102 patients who were treated with PCI after admission to our hospital from January 2020 to December 2020 were retrospectively analyzed. All the patients were followed up for 24 months to evaluate their long-term prognosis. The occurrence of cardiovascular and cerebrovascular events in all the patients was recorded. Cardiovascular and cerebrovascular events refer to a series of diseases or conditions of the heart and the cerebrovascular system, including sudden cardiac death. Patients with cardiovascular events were assigned to the exposed group, while those without cardiovascular events were included in the nonexposed group. The left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), left ventricular mass index (LVMI), left ventricular remodeling index (LVRI), left ventricular ejection fraction (LVEF), standard deviation of time to peak of left ventricular 16 segments (Tmsv16-SD), maximum time difference (Tmsv16-Dif), and difference between the 3DE index and the TYG index were collected. Logistic regression analysis was performed on the indicators with differences to analyze the influencing factors of the long-term prognosis of patients after PCI. The receiver operating characteristic (ROC) curve was drawn. The sensitivity, specificity, area under the curve (AUC), and Youden index were calculated. The best predictive cutoff value was determined. The predictive value of the 3DE index and the TYG index, either alone or in combination, was observed for long-term prognosis after PCI. The relationship between the 3DE index and the TYG index was explored. Result: The 2-year follow-up results showed that 22 patients experienced cardiovascular events, and they were included in the exposed group, accounting for 21.57%. The remaining 80 patients without cardiovascular events were included in the nonexposed group, accounting for 78.43%. A significant difference was found in creatinine (Cr), high-density lipoprotein cholesterol (HDL-C), LVEDV, LVESV, LVMI, LVRI, LVEF, Tmsv16-SD, Tmsv16-Dif, and the TYG index between the exposed group and nonexposed group (p < 0.05). Cr, HDL-C, LVEDV, LVESV, LVMI, Tmsv16-SD, Tmsv16-Dif, and the TYG index in the exposed group were higher than those in the nonexposed group (p < 0.05). The exposed group also had lower LVRI and LVEF than the nonexposed group (p < 0.05). Logistic regression analysis of the indicators with differences showed that Cr, HDL-C, LVEDV, LVESV, LVMI, LVRI, LVEF, Tmsv16-SD, Tmsv16-Dif, and the TYG index were the major factors that affect the long-term prognosis of patients after PCI, with odds ratio values >1. Correlation analysis showed that the TYG index was positively correlated with LVEDV, LVESV, LVMI, Tmsv16-SD, Tmsv16-Dif, and the TYG index (r = 0.565, 0.678, 0.696, 0.702, 0.788, 0.804, p < 0.05). Moreover, it was negatively correlated with LVRI and LVEF (r = –0.580, –0.674, p < 0.05). The sensitivity and specificity of the 3DE index combined with the TYG index in predicting long-term prognosis after PCI were 0.818 and 0.950, respectively, which were significantly higher than those of the 3DE index or the TYG index alone. The Youden index was 0.768, the AUC value was 0.922, and the optimal threshold was 36.64. Conclusion: The 3DE index and the TYG index were influencing factors for the long-term prognosis of patients after PCI, and a correlation existed between the 3DE index and the TYG index. The 3DE index combined with the TYG index can improve the predictive efficiency of the long-term prognosis of patients after PCI.