Objective To investigate the prevalence of age-related cataract and the treatment rate among adults aged 50 years or older in the Nagqu Prefecture of Tibet. Methods Cluster sampling was used in randomly selecting individuals aged 50 years or older in 11 counties in the Nagqu Prefecture of Tibet. The participants received a questionnaire, a visual acuity test and a clinical ocular examination. The status of the cataract surgery was also evaluated. The relationship between the prevalence of age-related cataract and age was analyzed with a chi-square test. The relationship between the prevalence of age-related cataract and gender was also analyzed with a chi-square test. Results 1 760 people were eligible for the examination but only 1 603 people were examined. The response rate was 91.08%. The prevalence of age-related cataract among adults aged 50 years or older in the Nagqu Prefecture of Tibet was 46.48%. Prevalence significantly increased with age(χ²=298.195, P＜0.01). Prevalence was higher in women than men, but the difference was not statistically significant (χ²=3.598, P>0.05). The treatment rate was 23.00%. Conclusion The prevalence of age-related cataract among adults aged 50 years or older in the Nagqu Prefecture of Tibet was much higher than in other areas of China. By contrast, the percentage of those treated was much lower. Cataract is a serious public health problem in Tibet.