Abstract: Objective: To assess left atrial geometric remodeling by three-dimensional echocardiograhpy in patients with non-valvular atrial fibrillation (NVAF), and to explore the application value of left atrial sphericity index (LASI) in predicting thrombosis risk in patients with NVAF.Methods: A total of 241 patients with NVAF enrolled for radiofrequency ablation of atrial fibrillation and/or left atrial appendage occlusion in the First Affiliated Hospital of Guangxi Medical University from January 2020 to June 2022 were collected, including 92 patients (38.2%) in the spontaneous echo contrast/thrombosis (SEC/TH) group and 149 patients (61.8%) in the non-SEC/TH group.The clinical data and echocardiographic parameters of the two groups were compared to analyze the factors affecting SEC/TH.The receiver operating characteristic (ROC) curve was used to analyze the predictive value of each parameter for thrombosis risk.Results: Left atrial diameter, left atrial volume index (LAVI), left atrial two-dimensional sphericity index (2D-SI) and three-dimensional sphericity index (3D-SI) in the SEC/TH group were higher than those in the non-SEC/TH group (all P< 0.05).Multivariate logistic regression analysis showed that 3D-SI was an independent risk factor for SEC/TH (OR=7.911, 95% CI:4.168-15.019, P< 0.001).ROC curve analysis showed that the sensitivity and the specificity of 3D-SI predicting SEC/TH were 86.96% and 64.43%, respectively.The area under ROC curve (AUC) of SEC/TH predicted by 3D-SI was 0.839 (95% CI:0.794-0.889), which was larger than 0.788 (95% CI:0.731-0.838) of 2D-SI, 0.710 (95% CI:0.649-0.767) of LAVI and 0.598 (95%CI:0.534-0.661) of CHA₂DS₂-VASc score (all P< 0.05).Conclusion: LAVI is a sensitive indicator for predicting the risk of intra-atrial thrombosis in patients with NVAF, and it is superior to traditional LAVI.3D-SI shows a better predictive value for the risk of thrombosis in patients with NVAF than 2D-SI.