Due to the superiority on the reduction of pollutant emissions by applying superfine pulverized coal with air-staged combustion and oxygen-enriched combustion, it has attracted more and more attention. Grinding process plays a crucial role in the variation of the physicochemical properties of raw coal. In this paper, the different scales of pore structures changing with particle size were investigated. The varying principle of pore structures during the grinding process was discussed. Our results indicate that as the particle size decreases, it has more developed pore structures and especially the concentration of micro-pores increases, which provide larger specific surface area and porosity that are beneficial to heat and mass transfer. Furthermore, the effect of particle size on the distributing characteristic of flash pyrolysis products by PY-GC-MS is studied, combining the analysis of carbon containing functional groups. Particle with smaller size has a larger content of oxygen containing functional groups and less concentration of C-C and C-H. Compared to HN coal, the proportion of aliphatic compounds in total release quantity is higher in NMG coal. In addition, the concentration of oxygen-bearing organic compounds first increases and then reduces, and it reaches to the maximal at around 14 mu m.