Aim To observe the level of interleukin-17A (IL-17A) in patients with atrial fibrillation (AF), to assess its clinical value of thrombotic events in AF patients. Methods 67 controls (38 males and 29 females, average age 60.37±9.51 years), 65 patients with paroxysmal AF (35 males and 30 females, average age 58.92±8.59 years), and 88 patients with persistent AF (57 males and 31 females, average age 61.45±8.32 years) were enrolled in the present study, the expression of IL-17A was measured, then judged by creating the receiver operating characteristic curves (ROC). Serum levels of MMP-9, procollagen type Ⅲ and the left atrial ejection fraction (LAEF) were examined and compared. The patients with AF who were complicated by thrombotic events were followed-up, levels of IL-17A were further analyzed to assess the predictive value for thrombotic events in patients with AF. Results The level of serum IL-17A was increased in patients with AF. Area under the ROC of IL17A was 0.784 (P＜0.01), the sensitivity was 78.6%, the specificity was 69.1%. In the patients with AF who were complicated by thrombotic events, the level of serum IL-17A was significantly increased, while it was markedly decreased after regular anticoagulant therapy. The increased IL-17A level was significantly correlated with the levels of MMP-9, procollagen type Ⅲ and LAEF. Conclusion IL-17A might promote AF and thrombus event in AF patients.