The aim of this study was to elucidate the speciation of PM2.5 and proportion of each typical speciation via calculation of chemical mass balance. The results from elemental and morphological analyses showed that PM2.5 consisted of diverse components mainly including O, Fe, Ca, Al, Si, and trace elements K, Na, Pb, S, and Cl. These components mainly existed in spherical, cubic, polyhedral, flake-like and bulk-like particles. Through examining the chemical composition and distribution property of main components in typical particles, Fe, Ca and O were determined to present in the speciation of Fe2O3–CaO from melting process, while Al, Si and O existed in the speciation of xAl2O3-ySiO2 from fuel fly ash. K, Na, Pb and Cl could exist in the speciation of KCl, NaCl and PbCl2 respectively from chlorination reactions. Moreover, Ca, K, Pb, O and S could form sulfates of CaSO4, K2SO4 and PbSO4 respectively. Calculation of O, S and Cl equilibrium in PM2.5 indicated that Fe2O3–CaO accounted for about 30.63%, xAl2O3-ySiO2 accounted for about 7.02%, K(Pb/Na)Clx accounted for about 41.29%–49.77%, and K2(Ca/Pb)SO4 accounted for about 21.05%–12.57%.