Objective: To evaluate the association of short-term fine particulate matters (PM2.5) exposure and blood pressure in children and adolescents. Methods: A total of 144 813 junior and senior middle school students who participated in the physical examination in the 2017-2018 academic year in a northern city of China, with complete record of demographic characteristics, blood pressure and no history of heart and other important organ diseases were selected as the study subjects. Data on PM2.5 and other pollutants and meteorological data were obtained from the nearest air quality and meteorological monitoring stations of each schools. A generalized linear mixed effect model was used to analyze the association between short-term exposure of PM2.5 and blood pressure. Results: The 6 day average concentration of PM2.5 (lag05) increased by 10 μg/m 3 was associated with an increase of 0.177(95%CI=0.148-0.207)mm Hg (1 mm Hg=0.133 kPa) in systolic blood pressure and 4.4%(OR=1.044, 95%CI=1.030-1.058) increase of the prevalence of high systolic blood pressure. And it was also associated with -0.021(95%CI=-0.040--0.002)mm Hg decrease in diastolic blood pressure, but had no significant correlation with the prevalence of high diastolic blood pressure. In general, a 10 μg/m 3 increase of PM2.5 was associated with 3.3% increase in the prevalence of high blood pressure (OR=1.03, 95%CI=1.02-1.05), and difference of boys and girls were found in different lagged days (P<0.05). Conclusion Short-term exposure of PM2.5 is associated with increased systolic blood pressure and prevalence of high blood pressure among children and adolescents. Attention should be paid to the prevention of short-term exposure of PM2.5 to protect the health of children and adolescents.