〔Abstract〕 Objective To explore the causal relationship between rheumatoid arthritis(RA) and iron deficiency anemia(IDA) in European population by two-sample Mendelian randomization analysis. Methods The single nucleotide polymorphisms(SNPs) of RA and IDA were analyzed using public genome-wide association studies(GWAS).The inverse variance weighting method(IVW) was used as the main analysis method to evaluate the causal effect of RA on IDA.MR-Egger method, weighted median method(WM),weighted model method and simple model method were used as regression supplements to evaluate the robustness of sensitivity analysis results.The heterogeneity function was used to calculate theP-value to test the heterogeneity, and the intercept term intercept was used to test the level pleiotropy. Results In the FINNGEN database at the genome-wide level, strong-related SNPs that removed linkage disequilibrium and met theP<5.0×10-8by Mendelian randomization analysis were selected.After integrating exposure and outcome data, 31 SNPs were obtained as the final effective instrumental variables.IVW showed that RA was a risk factor for IDA(the risk of IDA in RA patients was 1.064 times higher than that in non-RA patients,OR=1.064,95%CI:1.028-1.103).The weighted median method and MR-Egger method results supported the positive correlation between RA and IDA.The intercept value was close to 0,indicating that there was no horizontal pleiotropy between exposure and outcome.The heterogeneity function′sP<0.05 indicated that there was heterogeneity between exposure and outcome, but the random effect model test showedP<0.05,indicating that even if there was heterogeneity in causality, the overall trend was stable. Conclusion RA is a risk factor for IDA,and there is a positive correlation between RA and IDA.