Objective: Two-dimensional spot tracking (2D-STI) combined with real-time three-dimensional ultrasound (RT-3DE) was used to evaluate the right atrial function in patients with atrial fibrillation (AF) combined with moderate and severe tricuspid regurgitation, and to explore the risk factors for the occurrence of moderate and severe tricuspid regurgitation in these patients. Methods: A total of 134 patients with paraphylaxis AF who were admitted and diagnosed in the Department of Cardiology of our hospital from January 2023 to November 2023 were selected, including 99 patients with mild tricuspid valve regurgitation (Group A), 35 patients with moderate and severe tricuspid valve regurgitation (group B), and 41 healthy patients in the same period as the control group. Clinical data, conventional echocardiographic parameters [right atrium diameter (RAD1), right atrium diameter (RAD2), tricuspid annulus diameter (TVD) and tricuspid lobe closure height (TVH), etc.], 2D-STI parameters [right atrium storage strain (RASr), duct stage strain (RAScd) and auxiliary pump stage strain (RASct) were compared among the three groups. ] and RT-3DE parameters [right atrial maximum volume index (RAVImax), minimum volume index (RAVImin), pre-systolic volume index (RAVIpre), passive emptying score (pasEF) and active emptying score (actEF)]. Binary Logistics regression analysis was applied to explore the risk factors of AF combined with moderate and severe tricuspid regurgitation, and ROC curve was drawn to analyze the predictive value of independent risk factors for these patients. Results: Compared with control group, RASr, RAScd, RASct, pasEF and actEF in group A were decreased, RAVImax, RAVImin and RAVIpre were increased, the differences were statistically significant (all P < 0.05). Compared with control group and group A, RASr, RAScd, RASct, pasEF and actEF in group B were decreased, while RAVImax, RAVImin and RAVIpre were increased, with statistical significance (all P < 0.05). Multivariate analysis showed that TVD, RASr and RAVImin were independent risk factors for AF with moderate and severe tricuspid regurgitation. ROC curve analysis showed that the areas under the curve predicted by TVD, RASr and RAVImin were 0.9, 0.88 and 0.774, respectively. Conclusion: Right atrium remodeling occurs in patients with atrial fibrillation and tricuspid regurgitation. TVD, RASr and RAVImin are independent risk factors for moderate to severe tricuspid regurgitation in patients with atrial fibrillation.