Objective: To investigate the prevalence and associated factors of unaided visual impairment and myopia among primary and secondary school students in Yunnan Province, and to provide scientific basis for myopia prevention. Methods: The study was conducted among primary and secondary school students in Mangshi, Yunnan Province from March to August, 2014. All the 7 681 subjects underwent detailed eye examinations and a questionnaire survey. Myopia was defined as spherical equivalent value of less than -0.5 diopters. Unaided visual impairment was analyzed on the basis of the better and the worse-seeing eye, respectively. Results: The prevalence of myopia and high myopia were 39.1% and 0.6%. The prevalence of unaided visual impairment was 11.4% based on the worse-seeing eye. Refractive errors accounted for 87.3% of the participants with unaided visual impairment. Prevalence of myopia was higher in girls than in boys (χ2=29.74, P<0.01), but there was no gender difference in high myopia (P=0.19). The prevalence of myopia and high myopia increased significantly with increasing age (χ2=351.23, 22.56, P<0.01). Besides, prevalence of myopia was 63.7% in Dai nationality students and 36.6% in Yi nationality students (χ2=78.14, P<0.01), which was higher than other ethnic minorities. After adjusting for the effects of sex, age and ethnicity, the presence of myopia was associated with increasing height (OR=1.02, 95%CI=1.01-1.03), computer use (OR=1.17, 95%CI=1.03-1.32), having a myopic father (OR=1.56, 95%CI=1.24-1.94), having a myopic mother (OR=1.33, 95%CI=1.08-1.63) and more time reading(OR=1.18, 95%CI=1.09-1.28). High myopia was found to be more prevalent in children who had a myopic father (OR=3.98, 95%CI=1.72-9.22) and using computers (OR=2.31, 95%CI=1.17-4.57). Conclusion Myopia and unaided visual impairment is prevalent in school students in rural China (Yunnan), though the prevalence is relatively lower compared with other areas in China. Attention should be paid to the formulation and input of primary eye care policies.