Fine particles ($PM_{2.5}$) were collected and analyzed from April 2010 through January 2011 in Chungju to investigate the characteristics of $PM_{2.5}$ and its ionic species. The annual mean concentrations of $PM_{2.5}$, ${SO_4}^{2-}$, $NO_3{^-}$, and $NH_4{^+}$ in the particulate phase were 40.84, 7.61, 7.14 and $3.74{mu}g/m^3$, respectively. $PM_{2.5}$ concentrations were higher in fall and spring than in winter and summer. The elevated concentrations episodes are the main factor that enhanced the $PM_{2.5}$ concentrations in the fall. Among the major ionic species ${SO_4}^{2-}$ showed the highest concentration, followed by $NO_3{^-}$ and $NH_4{^+}$, $NO_3^-$ exhibited higher concentrations during the winter, but ${SO_4}^{2-}$ and $NH_4{^+}$ were not showed seasonal variation. The high correlations were found among $PM_{2.5}$, ${SO_4}^{2-}$, $NO_3{^-}$ and $NH_4{^+}$ during all seasons except for spring. The evaluation of backward trajectories and meteorological records show that the highest $PM_{2.5}$ concentration levels occurred during W-NW weather conditions, which influenced by the emission sources of China area. The low pollution levels generally occurred during E-S weather conditions, which influenced by the East Sea and south of the Yellow Sea. The elevated $PM_{2.5}$ mass concentrations arouse the concentration of $NO_3{^-}$, but no effects on ${SO_4}^{2-}$ and $NH_4{^+}$.