Microwave heating (MW) and freeze fracturing (FF) have been widely used for enhancing the permeability of coal reservoirs. In this paper, the effects of combined MW-FF treatments on coals are experimentally investigated through nuclear magnetic resonance. T 2 distributions and fractal dimensions of coals under MW, FF, and the combined MW-FF treatments are compared and analyzed. The results show that the T 2 area, porosity, and fractal dimensions of coals increase to varying degrees after MW, FF, and MW-FF treatment. The T 2 spectrum peaks increase from 2 to 3 and macrofractures can be observed after the coal was treated with the combined MW-FF treatments.However, these phenomena are not observed under MW or FF treatment. The combined MW-FF treatments can effectively fracture coals with less microwave energy and less liquid nitrogen freezing cycle owing to its intensive thermal shock fracturing. Therefore, the combined MW-FF treatment is favorable for fracturing the coals and hence favorable for the CBM production.