Abstract: The pyrolysis characteristics of the coals and their blends in an inertia atmosphere were investigated using a thermo-gravimetric apparatus with a on-line infrared-spectrum analyzer. The influence of coal rank, blend ratio and heating rate on the pyrolysis of coal blends was examined. The experimental results show that the pyrolysis characteristics of coal blends are similar to that of single coal, but the yield of gas is not the simple addition of single coal's. Due to the interaction of different coals of the blends, there is a difference in the gas yield between coals and the blends. By investigating the infrared spectrogram, it is discovered that the low rank coal has an important role in the pyrolysis of the blends. The beginning pyrolysis temperature decreases and the yield of gas increases with increasing the proportion of low rank coal.