Abstract： Objective To assess causal associations between specific gut microbiota and different types of cancer by using the two-sample Mendelian randomization(MR)analysis method.Methods On the basis of summary statistics of gut microbiota from a genome-wide association study(GWAS)conducted in German population(n=8956),single nucleotide polymorphisms(SNPs)that were significantly associated with 430 gut microbiota features were extracted as instrumental variables(Ⅳs).Summary statistics from the GWAS of 17 types of cancer were used as outcomes.Two-sample MR analysis was used to explore the causal relationship between gut microbiota and pan-cancer,where the analysis results were dominated by inverse variance weighting.Meanwhile,sensitivity analyse of heterogeneity and horizontal pleiotropy test were done to keep the stability of results.Results The genetic susceptibility of 17 gut microbiota features was causally associated with the occurrence and development of 11 different types of cancer,respectively.Conclusion By exploring the causal relationship between different gut microbiota features and pan-cancer,this study has found a potential causal relationship between specific gut microbiota features and cancer,and these gut microbiota may become new biomarkers to provide new ideas for cancer prevention,early screening,and treatment.