A series of experiments on co-combustion of the retorting residue of Huadian oil shale and cornstalks at different blending proportions were performed on a Pyris-1 thermogravimetric analyzer (TGA) to investigate the mechanism of the reactions involved. Moreover, the abrupt curvature changes of thermogravimetric (TG) curves and the multi-peaks and -shoulders of differential thermal gravity (DTG) curves for the blends were analyzed based on a simulation model of multi-component combustion. Results showed that the processes of combustion represented a multistage procedure of a clearly segmented nature. The processes can be divided into three stages of different temperature ranges: the first stage (135-380 degrees C), the second stage (380-560 degrees C) and the third stage (560-700 degrees C). With increasing blending ratio of cornstalks, the free energy of activation of combustion in the first and second stages is much lower than that in the third stage. Meanwhile, the continuous reaction processes of the samples combustion were analyzed by the Kissinger-Akahira-Sunose (KAS) kinetics model. Results showed that the activation enthalpy, activation entropy and free energy of activation of the samples combustion in its different stages varied. Moreover, with the addition of cornstalks, the portion of the ordered structure of activated molecules increased and the combustion characteristics of the retorting residue improved.