Objective In this study，we performed two sampie Mendelian Randomization to infer a causal association between Gastroesophageal reflux(GERD) and Atrial fibrillation(AF)，it can effectively avoid the problems such as reverse causation and confounds in traditional epidemiology. Methods We used the Summary data of GERD and AF from published Genome wide association study(GWAS) of European Individuals. Single Nucleotide Polymorphisms (SNPs) were extracted as Instrumental Variables (IVs).The main MR methods include Inverse Variance [] Weighted(IVW)，Weighted Median(WME)，MR-Egger，Simple Mode，and Weighted Mode.In addition，we used the sensitivity analysis such as MR-PRESSO，Cochran's Q test etc. Results The IVW shows a causal association between GERD and AF(P<0.0001，OR=1.16，95%CI:1.10-1.23).The WME shows P＜0.0001，OR=1.20，95%CI:1.11-1.30；Simple Mode shows P=0.01，OR=1.34，95%CI:1.07-1.69；Weighted Mode shows P=0.02，OR=1.33，95%CI:1.06-1.66. Conclusion This study based on genetic data supports the causal association between GERD and AF. The occurrence of GERD could increase the risk of AF.