Background Pterygium is a common ophthalmic disease and an important public health problem. It may be affected by many factors such as age, gender, ultraviolet radiation exposure, and time spent outdoors. This study aimed to investigate the prevalence of pterygium and evaluate the risk factors for the development of pterygium in the aged rural population of Beijing. Methods The investigation is a population-based cross-sectional study. Participants from 198 villages of 13 suburban districts, aged 55-85 years old, were invited to complete a medical record, and 37 067 individuals were taken external ocular and fundus photos at Beijing ocular disease survey in 2008-2009. The information was uploaded by Internet and diagnosed with stages and grades by ophthalmological specialists. The prevalence, stages and grades of pterygia were observed. Results Of the 37 067 individuals, 1395 (3.76%) had pterygium. There was a significantly higher prevalence in male (5.13%) than in female (3.17%, P=0.000). The prevelence rate increased obviously with ages (X-2=7.939, P=0.019) in rural Beijing. The average prevalence of 5.91% in Daxing and Fangshan districts with low latitude and low precipitation was significantly higher than that in Miyun and Huairou districts with high latitude and deep precipitation (3.17%, P=0.000). The majority of the pterygia (43.5%) were in active stage and 46.5% pterygia involved pupil area corneas. Conclusions There is a statistically significant association between latitude and precipitation of habitation region and pterygium formation. Solar radiation, especially ultraviolet exposure represents a significant environment hazard to pterygium development. Chin Med J 2010;123(13):1699-1701