In summary, this study revealed that Th17 cells and their related cytokines (IL-17, IL-6, MMP9) were significantly increased, while Tim-3 + cells and their related cytokines (Tim-3, Gal-9) were significantly decreased in the peripheral blood of AF patients, and Th17 cells and their cytokines were negatively correlated with Tim-3 + cells and their cytokines, and involved in the development of the course of AF. Here, MMP9 is linked to atrial fibrillation.