Two chinese bituminous coals used in coal-fired power plants are combusted under air conditions in a lab-scale drop tube furnace. The effects of minerals transformation on the formation of PM 2.5 are investigated during the combustion of coal blends. The collected PM were subjected to Computer controlled scanning electron microscopy (CCSEM) and High-resolution transmission electron microscopy(HRTEM) coupled with energy dispersive X-ray spectroscopy (EDX) analysis for determination of chemical species within them. The results show that PM 2.5 emissions are not linearly related to the wt.% of the parent coal or coal blends. Transformations of fine Si-Al mineral grains provided by the minerals in coal XQ into coarse particles (>2.5 μm in diameter) are responsible for the reduction of PM1-2.5 during the combustion of coal blending. The transformed fine Si-Al particles are captured by the coarse Ca-Mg-Al-Si provided by the minerals in coal HT to form larger Ca-Mg-Al-Si particles (>2.5 μm in diameter). Increasing Ca and Mg concentration in coal blends enhances the liquid concentration produced during combustion and hence affects the emissions of PM1 and PM1-2.5.Through adjusting the mineral compositions in coal blends, the reduction of PM1 and PM1-2.5 emissions can be achieved during combustion.