Objective To investigate the causal relationship between gastroesophageal reflux disease(GERD)and different phenotypes of asthma based on Mendelian randomization(MR).Methods The dataset was pooled by genome-wide association studies(GWAS),in which the GERD data contained 602 604 cases,the unspecified asthma data contained 156 078 cases,139 591 cases of obesity-associated asthma,138 474 cases of pediatric asthma,140 308 cases of allergic asthma and 136 633 cases of eosinophilic asthma.The inverse va-riance weighting method was used as the main method of MR analysis,and the weighted median method,sim-ple model,weighted models and MR-Egger conducted the supplement,and the sensitivity analysis was carried out to assess the stability of the results.Results The MR analysis showed that unspecified asthma(OR=1.61,95%CI:1.45-1.77,P<0.01),obesity-related asthma(OR=2.40,95%CI:1.98-2.90,P<0.01),Childhood asthma(OR=1.56,95%CI:1.25-1.94,P<0.01)and allergic asthma(OR=1.47,95%CI:1.25-1.74,P<0.01)present the forward cause effect,but eosinophilic asthma had no causal relation with GERD(OR=1.31,95%CI:0.95-1.81,P=0.10).The sensitivity analysis showed that the horizontal pleiot-ropy and heterogeneity in the results did not exist.Conclusion GERD could lead to an increased risk of un-specified asthma asthma,obesity-associated asthma,pediatric asthma and allergic asthma,while the effect on eosinophilic asthma is not significant.