Objective: To examine the association between leukocyte telomere length and cataract using bidirectional Mendelian randomization (MR) approach, so as to provide the basis for early diagnosis and prevention of cataracts. Methods: Leukocyte telomere length data were collected through a meta analysis of genome-wide association studies (GWAS), including 78 952 participants, and the GWAS data of cataract were collected through the UK Biobank, including 8 890 cases and 454 120 controls. A bidirectional MR analysis was performed using the inverse-variance weighted (IVW) method, and single nucleotide polymorphisms (SNPs) which were associated with leukocyte telomere length were selected as instrumental variables. The heterogeneity was assessed using the Cochran's Q test, the horizontal pleiotropy was assessed using the MR-Egger regression and the outlier was verified with the leave-one-out and MR-PRESSO test. Results: Forward MR analysis results showed that shortened leukocyte telomere length had an increased risk of cataract (OR=0.991, 95%CI: 0.990-0.997). Reverse MR analysis results showed no statistically significant association between leukocyte telomere length and cataract (P>0.05). Cochran's Q test detected no heterogeneity, and neither the MR-Egger regression nor the MR-PRESSO test revealed horizontal pleiotropy of instrumental variables (both P>0.05). Leave-one-out analysis showed robustness of the MR analysis results. Conclusion Shorter leukocyte telomere length might be associated with increased risk of cataract.