Objective To assess the causality between 14 malignant tumors and hypertension.Methods Publicly available datasets from genome-wide association study were used,from which independent genetic variants strongly associated with hypertension and 14 malignant tumors were extracted as instrumental variables for bidirectional Mendelian randomization(MR)analysis,including random effect inverse variance weighted(IVW),simple mode,weighted median,weighted mode and MR-Egger to evaluate the causal effect.Sensitivity analysis was used to test the validity and robustness of the analytical results,and multivariate MR method was used to further control for the effects of confounding factors.Results In the MR analysis of malignant melanoma and hypertension,the study included a total of 11 single nucleotide polymorphisms(SNPs)strongly associated with malignant melanoma.After Bonferroni correction,the IVW-based results showed a causal relationship between malignant melanoma and hypertension(OR=1.67,95％CI:1.27-2.21,P＜0.001).Cochran's Q test,Mendelian randomization pleiotropy residual sum and outlier test and MR-Egger intercept test showed that there were no outliers and no horizontal pleiotropy among the instrumental variables,and the sensitivity analysis of the leave-one-out method showed that there was no single SNP that had a significant impact on the overall results.In the analysis of hypertension and leukemia,the preliminary analysis results showed that there may be a relationship between the two,but after adjusting for confounders,the effect of hypertension on the risk of leukemia was no longer significant.Conclusion Malignant melanoma may be a risk factor in the development of hypertension.