The aim of this study was to investigate the detection rate of left atrial appendage thrombus (LAAT) formation in non-valvular atrial fibrillation (NVAF) patients using three methods and the efficacy of combined electrocardiogram (ECG) and Computed Tomography Angiography (CTA) in the diagnosis of LAAT. A total of 80 NVAF patients who underwent Transesophageal echocardiography (TEE) at our hospital from August 2018 to August 2022 were included in the study. The baseline data of patients were observed, and the positive rates of LAAT formation by ECG, CTA, and TEE were compared. The efficacy of combined ECG and CTA in the diagnosis of LAAT was also evaluated. Among the 80 NVAF patients, 23 were LAAT positive and 57 were LAAT negative. There were statistically significant differences between the two groups in terms of age, body mass index (BMI), N-terminal prohormone of brain natriuretic peptide NT-probNP, fibrinogen, CHA2DS2-VASC [congestive Heart Failure, Hypertension, Age (75 or older), diabetes mellitus, stroke, vascular disease, age (65-74), sex category] score, paroxysmal atrial fibrillation, renal insufficiency, D-dimer, heart failure, and serum uric acid (p<0.05). The positive rate of LAAT detected by ECG combined with CTA was closest to the gold standard TEE, but the difference was not statistically significant (p>0.05). Statistically significant differences were found between LAAT positive and negative patients in various parameters related to left atrial and left ventricular dimensions and function (p<0.05), while some parameters showed no significant differences (p>0.05). ECG combined with CTA has a high diagnostic value for LAAT formation in NVAF patients, with a high degree of confidence and reduced patient intolerance. The sensitivity, accuracy, and negative predictive value of ECG combined with CTA for the diagnosis of LAAT formation in NVAF patients are high and have good predictive value.