Abstract: To investigate the exposure characteristics and potential sources of fine particulate matter (PM_2.5), a panel study was conducted for children in a primary school in Tianjin. Thirty-six children aged from 9 to 12 were selected, and their personal exposures to PM_2.5 were monitored in summer (May 17-June 24) and winter (November 8-December 3) in 2010. The results showed that the mass concentrations of personal PM_2.5 exposure in winter ((122.4±42.3)μg/m³) were higher than those in summer ((74.7±29.5)μg/m³), which might be related to heating in the cold season. Significant correlations were found between Si and Al, as well as Zn, Pb and Mn in both monitoring periods by Spearman correlation analysis. The total concentrations of SO₄^2- and NO₃^- accounted for 43.3% of PM_2.5 in summer, and 39.5% in winter. The ratio of NO₃^-/SO₄^2- was 2.3 in summer, indicating that mobile sources were the principal source of personal PM_2.5 exposure; while in winter, the ratio was 0.6, indicating that stationary sources were the primary contributor. Concentrations of organic carbon (OC) and elemental carbon (EC) in winter were higher than those in summer, which was consistent with the seasonal trend of PM_2.5. Results of source apportionment analysis showed that secondary sources, vehicle exhaust, soil, industrial sources and vehicle additives contributed 30.4%, 28.9%, 12.8%, 20.8% and 7.1%, respectively, to PM_2.5 exposure of children in summer; whereas in winter, secondary sources, vehicle exhaust, soil, industrial sources, coal combustion and road dust contributed 26.5%, 24.5%, 13.7%, 10.3%, 19.9% and 5.1%, respectively.