The pyrolysis characteristics of low quality mixing coal are investigated by thermal analyses,in which the coal is mixed by coal gangue and washed middling coal. The sample is five kinds of mixing materials which their proportion is 1:4, 2:3, 1:1, 3:2, 4:1. The experiment showed that 2:3 coal sample is to achieve best result to the pyrolysis; The pyrolytic characteristic temperatures and the best mixing proportion are obtained. The activation energy and frequency factor of samples are acquired by analyzing combustion kinetics.