Objective 　To investigate the effect of radiofrequency ablation (RFA) on miRNA expression in coronary sinus blood (CSB) of patients with atrial fibrillation (AF), especially after the termination of AF by RFA. And try to identify the possible miRNAs which can play real regulatory role in AF, so that to find the pathogenesis of AF and possible miRNA targets for intervention. Methods 　Thirty AF patients (paroxysmal, persistent and permanent AF, 10 each) were enrolled, alongside of 10 healthy subjects as controls. Peripheral blood (PB) samples were obtained before and 3 months after RFA, respectively. The total RNA was extracted and hybridized with the microRNA chips (microRNA v18.0), and the differential expressions of miRNA and clustering analysis in whole genome were performed with Volcano Plot and tMEV software respectively, and validated by Real-time PCR. The target gene of miRNAs was analyzed by retrieving the mirbase, miranda and targetscan databases. The important miRNAs were undergone with dual luciferase binding experiment to analyze and validate target genes. Results 　Comparing the CSB with PB of patient-self before RFA, 142 miRNAs expressed differently, of which 6 up-regulated and 8 down-regulated significantly (P<0.05). When comparing the PB of patients-self after and before RFA, 3 miRNAs up-regulated and another 3 down-regulated in above mentioned up-regulated 6 miRNAs, and miR-1266 was down-regulated 204.17-fold. Of 8 down-regulated miRNAs mentioned above, 7 were down-regulated again after RFA, and miR-3664-5p down-regulated 44.66-fold, while miR-574-3p up-regulated 5.25fold. SCN5A was the target gene of miR-1266, and CACNA1C was the target gene of miR-4279 confirmed by luciferase binding experiments. Conclusions 　The differential expression of miRNAs in CSB may directly reflect the regulatory status of miRNAs in cardiomyocytes in AF attack. RFA can reverse or change the abnormal expressions of miRNAs in CSB of AF patients in pro-RFA. The miRNAs which altered significantly before and after RFA, or regulate multi-ion channel proteins simultaneously, like miR-1266, may become a future target for AF intervention. DOI: 10.11855/j.issn.0577-7402.2016.10.06