A comprehensive model accounting for intraparticle heat and mass transport phenomena, primary and secondary reaction processes was developed. Mass loss history, particle surface temperature history, and volatile product distribution of oil shale particles at different pyrolysis temperatures were favorably compared with experimental data. Particle size and reactor temperature would affect temperature and residue solid density distribution in oil shale particle. It was proved by the model that the increase of pore surface area in smaller oil shale particle may not be the main reason causing the decrease in oil yield and the increase in gas yield. Neglecting the variation of the residue solid density at different particle sizes, the model showed that with the increase of particle radius, the oil yield decreased and the gas yield increased. The effects of heating rate on the volatile product distribution might depend on intraparticle mass transport resistance.