Aim To evaluate the right atrial function by two-dimensional speckle tracking imaging (2D-STI) combined with real-time three-dimensional echocardiography (RT-3DE) in patients with triple vessel coronary artery disease (TVCAD) without myocardial infarction. Methods Fifty-six patients with TVCAD without myocardial infarction were selected and divided into two groups according to the results of coronary angiography:28 cases with a stenosis rate of 50%～75% and 28 cases with a stenosis rate of ≥75%. In addition, 30 healthy volunteers were screened as control group. RT-3DE was performed to obtain the parameters of right atrial volume (RAV_max, RAV_min and RAVp) and then calculated right atrial passive ejection fraction (RAPEF) and right atrial active ejection fraction (RAAEF), and the maximum of right atrial volume index (RAVI_max). 2D-STI was applied to measure right atrium strain rates during systole, early diastole and late diastole (RASRs, RASRe and RASRa). Correlation between 2D-STI parameters and N-terminal pro-brain natriuretic peptide (NT-proBNP), Gensini scores were analyzed by Pearson analysis. ROC curve analysis was used to evaluate the diagnostic value of 2D-STI, RT-3DE, and their combined use for right atrial function in TVCAD patients without myocardial infarction. Results Compared with control group, RAPEF and RASRe reduced in stenosis rate of 50%～75% group, while RAAEF and RASRa increased (all P＜0.05). Compared with control group and stenosis rate of 50%～75% group, RAPEF, RASRs, RASRe and RASRa decreased, while RAV_max, RAV_min, RAVp, RAVI_max and RAAEF increased in stenosis rate of ≥75% group (all P＜0.05). There was a significant correlation between 2D-STI parameters and NT-proBNP and Gensini scores. The area under the curve of right atrial function in TVCAD patients without myocardial infarction was 0.8,0.8917 and 0.9564 for 2D-STI, RT-3DE and their combined use, respectively. The diagnostic efficacy of the two methods was significantly higher when used in combination than when used alone, and 2D-STI was superior to RT-3DE. Conclusion When evaluating the right atrial function of TVCAD patients without myocardial infarction, the diagnostic efficacy of 2D-STI combined with RT-3DE is higher than that of using it alone, and 2D-STI is superior to RT-3DE.