Objective: To analyze the prevalence and trend of myopia among children and adolescents in Inner Mongolia from 2019 to 2021，so as to provide a reference for making scientific and effective prevention and controlling measures of myopia. Methods: By using the stratified random cluster sampling method, 555 093 children and adolescents were selected from 12 professional institutions in league cities of the whole region for remote vision examination and refractive examination. The refraction test was carried out under the condition of non-Ciliary muscle paralysis using a desktop automatic computer optometer. Chi-squared test and multivariate Logistic regression were used to analyze the myopia status of children and adolescents and its influencing factors. Results: From 2019 to 2021, the myopia rate of children and adolescents was 53.30%, 58.65% and 54.82%, respectively, the difference was statistically significant ( χ 2=991.70, P <0.01). The overall female myopia rate(58.82%) was higher than that of male (51.52%), and the differece was statistical significant ( χ 2=3 295.66, P <0.05). The myopia rates of boys and girls by year were 49.44% and 57.30%, 54.76% and 62.60%, 51.23% and 57.62%, respectively, and the differences were statistically significant ( χ 2=1 197.02, 922.31, 1 172.09, P <0.01). The overall myopia rate of urban students (59.42%) was higher than that of suburban counties (53.61%), and the difference was statistically significant ( χ 2=1 565.03, P <0.05). The myopia rates of children and adolescentss in urban and suburban counties were 59.20% and 50.79%, 60.26% and 57.88%, 58.95% and 53.36%, and the differences were statistically significant ( χ 2=1 150.80, 74.10, 529.25, P <0.01). The children and adolescents of learning stages were of statistical significance ( χ 2=92 402.39, P <0.05), and the overall myopia rate of senior school students was the highest, accounting for 83.57%. The difference of overall myopia rates of different age groups was of statistical significance ( χ 2=121 881.67, P <0.05), and the students in age group of 17 ranked the first (83.32%), those in age group of 5 ranked the last(15.52%). Conclusion From 2019 to 2021, the myopia rate of children and adolescents in the Inner Mongolia Autonomous Region increase first and then decrease, and the myopia rate in 2020 and 2021 is higher than that in 2019. The high incidence and low age of myopia are intensifying. The prevention and controlling of myopia among children and adolescents should be strengthened, so as to reduce the occurance of myopia.