Abstract: The mechanism underlying atrial fibrillation （AF） is not completely understood due to its complexity. In addition to anatomical structure of the heart, structural remodeling, electrical remodeling, autonomic nervous system regulation, and calcium ion （Ca²⁺） malfunctioning can also cause focal ectopic discharges and trigger AF. Moreover, triggering the incidence and persistence of reentrant AF through a reentry maintenance mechanism is also an important mechanism leading to AF. Further studies have found that the synthesis and degradation of related pathways, ion channel proteins and transporters can be changed through the role of microRNA （miR） inregulating messenger RNA. It not only affects the ionic current, leading to abnormal Ca²⁺ transport and cardiac electrical remodeling,but also influences fibroblasts, resulting in tissue fibrosis andstructural remodeling, and eventually inducing the incidence and maintenance of AF. Cardiac development, cardiomyocyte proliferation and substrate formation due to reentry mechanism causing AF were correlated with miR. MiR would become a novel biomarker for diagnosis of AF and a novel target for upstream treatment.