To determine the prevalence of and risk factors for myopia in primary school children in Chaoyang District, Beijing. This cross-sectional prevalence survey was conducted in September to October 2011 in 4 schools randomly chosen from among the 126 primary schools in Chaoyang District. Students were assessed with autorefractometry under cycloplegia and checked with retinoscopy for accuracy. Questionnaires were completed by the students' parents. Myopia was present in 36.7 ± 0.7% of 4249 students aged 5-14 years old. The prevalence of myopia in girls (38.6 ± 1.1%) was significantly higher than in boys (35.0 ± 1.0 %) (p = 0.015) and increased with age (p < 0.001), with the highest prevalence observed in children aged ≥11 years (67.5 ± 1.8%). After adjustment, having a myopic parent (aOR 3.10; 95% CI 2.49-3.86), incorrect reading posture (aOR 2.09; 95% CI 1.75-2.50), reading a book at a distance of <20 cm (aOR 1.60; 95% CI 1.16-2.21), studying at home for >3 h daily (aOR 1.50; 95% CI 1.12-2.01), studying for >1 h continuously (aOR 1.21; 95% CI 1.02-1.45), and reading extracurricular books that utilize a font larger than that used in textbooks (aOR 0.74; 95% CI 0.59-0.94) were all significantly associated with myopia. The prevalence of myopia among primary school children in Beijing increased with age, and was significantly higher in girls ≥10 years old. Myopia was significantly associated with parental myopia, reading posture, distance between the eyes and the book being read, font size used in extracurricular reading material, time spent studying at home, and the duration of continuous study time.