A finite difference method and the code Furnace of J.H. Kent were used to calculate the particle temperature and residence time in an entrained flow reactor. Then, three kinds of Chinese coals were pyrolyzed in the reactor. The auther analysed the chemical reaction mechanism of coal pyrolysis. Considered the coal pyrolysis as a parallel reactions of functional groups. Related the individual volatile species formation to elementary free radical steps. Developed a new volatile evolution model. The predictions agreed quantitatively with the experimental data of rapid pyrolysis in the overall weight loss and individual volatile species.