Objective: To analyze the current status, trend and predictors of thromboembolism risk assessment in patients hospitalized with non-valvular atrial fibrillation (NVAF) in tertiary hospitals in China. Methods: The study was based on data from the Improving Care for Cardiovascular disease in China (CCC)-Atrial Fibrillation (AF) project. About 10% of the tertiary hospitals in each geographic-economic stratum were recruited. Participating hospitals reported the first 10 to 20 patients with a discharge diagnosis of atrial fibrillation monthly. From February 2015 to December 2019, a total of 49 104 NVAF patients from 151 tertiary hospitals in 30 provinces, municipalities and autonomous regions were enrolled. Clinical data of the patients was collected. The proportion of NVAF patients receiving thromboembolism risk assessment, variations in the proportion between different hospitals, the time trend of the application of thromboembolism risk assessment, and the predictors of the application of thromboembolism risk assessment were analyzed. Results: The age of the NVAF patients was (68.7±12.1) years, 27 709 patients (56.4%) were male. Only 17 251 patients (35.1%) received thromboembolism risk assessment. The proportion varied substantially between hospitals with the lowest value of 0 and the highest value of 100%. Among the hospitals, which enrolled more than 30 patients, no patients received thromboembolism risk assessment in 18.4% (26/141) of the hospitals, more than 50% of the patients received thromboembolism risk assessment in 21.3% (30/141) of the hospitals, and all the patients received thromboembolism risk assessment in only 1 hospital. The proportion of NVAF patients receiving thromboembolism risk assessment was 16.2% (220/1 362) in the first quarter of 2015, and significantly increased to 67.1% (1 054/1 572) in the last quarter of 2019 (P<0.001). Patients' characteristics were associated with the application of thromboembolism risk assessment. The odds of receiving thromboembolism risk assessment was lower in male patients compared to female patients(OR=0.94,95%CI 0.89-0.99), lower in patients with acute coronary syndrome or other cardiovascular diseases compared to those with AF as the primary admission reason (OR=0.59, 95%CI 0.55-0.63, OR=0.52, 95%CI 0.45-0.61, respectively), and lower in patients with paroxysmal, persistent and long-standing/permanent AF compared to those with first detected AF (OR=0.62, 95%CI 0.57-0.67, OR=0.72, 95%CI 0.66-0.79, OR=0.57, 95%CI 0.52-0.64, respectively). The odds was higher in patients with a history of hypertension, heart failure, stroke/TIA, and previous anticoagulant therapy compared to those without the above conditions (OR=1.17, 95%CI 1.11-1.23, OR=1.18, 95%CI 1.07-1.30, OR=1.17, 95%CI 1.08-1.27, OR=1.28, 95%CI 1.19-1.37, respectively) (P all<0.05). Conclusion: Thromboembolism risk assessment was underused in patients hospitalized with NVAF in tertiary hospitals in China, and there were substantial variations between hospitals in the application of thromboembolism risk assessment. The application of thromboembolism risk assessment in tertiary hospitals has been improved in recent years, but there is still plenty of room for future improvement. Patients' characteristics could affect the application of thromboembolism risk assessment in China.