Abstract: Objective To investigate the relationships between left atrial volume index (LAVI) and atrial fibrillation (AF) after off-pump coronary artery bypass (OPCABG) and evaluate the predictive value of LAVI. Methods The clinical data of 97 cases of OPCABG from January, 2016 to December, 2017 were collected, they were examined preoperatively on transthoracic echocardiography, The left atrial volume was measured by three-dimensional ultrasound, and the height and weight were measured, and the Standardized Surface Area was calculated. All patients were divided into atrial fibrillation group and non-atrial fibrillation group. By compared the clinical relative factors of the two groups patients, analyzed the factors of LAVI, age, medical history, Premedicate, with AF after OPCABG According to LAVI ≥ 32 ml/m², the occurrence of atrial fibrillation between the two groups was compared. Results Univariate analysis showed that the age, left atrial volume index, in the AF group were significantly higher than that of the non-AF group, left ventricular ejection fraction in the AF group were significantly lower than that of the non-AF group (P<0.05). Multifactor analysis showed that the left atrial volume index was an independent predictor of atrial fibrillation after OPCABG. In patients with LAVI ≥ 32 ml/m², the incidence of atrial fibrillation increased significantly after OPCABG. Conclusion LAVI was an independent predictor of atrial fibrillation after OPCABG, effective prevention and timely treatment of postoperative atrial fibrillation, shortened hospital stay and improved prognosis.