The pore structure of coke under CO2 atmosphere was investigated by the carbon solution-loss reaction experiment. The results show that the pore size distribution of coke gradually changes from dispersion to relative concentration with the increase in carbon loss rate, but it tends to be dispersed again in the late stage of the reaction, and the pore volume and specific surface area also increase first and then decrease with the increase in carbon loss rate. Scanning electron microscopy results show that the evolution of coke pores is from the formation of micropores to the expansion of micropores, and finally the micropore and mesopores collapse to form a large number of string holes. The chemical bonds and functional groups of different reacted cokes were analyzed by Fourier-transform infrared spectroscopy. Furthermore, the microstructure of reacted cokes was analyzed by optical microscopy, and then the ordering of the affinity of different microstructures with CO2 was given. The volume hypothesis which was the theory about energy size of comminution was adopted to analyze the degradation behavior of reacted cokes. The breakage energy of reacted cokes was calculated by volume hypothesis, and the power consumption coefficient CK of different reacted cokes was determined by drum experiment, and then the degradation behavior of reacted cokes under different power consumptions was predicted.