Through thermogravimetric analysis technology, by using the Coats - Redfern integral method to deal with the same coal sample under different process conditions of coal, the reaction activation energy of coal combustion was studied. The results showed that using the Coats - Redfern integral method can only solve the high temperature period of activation energy of coal. The activation energy values of coal in high temperature period were influenced by various conditions, the activation energy values of coal were not consistent in the various conditions. The activation energy values of coal can be lowered under the complicated conditions, thus increase the self-ignition orientation of coal. Studying the activation energy of coal under various conditions can provide powerful basis for mine fire prevention.