In order to study the microstructure changes of hot semi-coke activated by pulverized coal under different atmospheres and temperatures, Raman spectroscopy was used to characterize the carbon frame structure of coal coke, X-ray photoelectron spectroscopy (XPS) was used to detect the surface functional groups of C and O, and solid state 13C nuclear magnetic resonance spectroscopy (13C-NMR) was used to characterize the carbon covalent bond. The three measurement methods were verified with each other to improve the reliability of the results, and the chemical structure of semi-coke was characterized from the microscopic level. The influence of temperature and atmosphere on the chemical structure and surface functional group evolution of coal coke in the mesothermal activation reaction was analyzed, and the mechanism of mesothermal activation was discussed on this basis. The results show that the activity of char at 600-900 ℃ can be significantly enhanced by both CO2 and water vapor, which may be caused by the combination of gas molecules and coal coke molecules to form carbonyl or carboxyl groups. Under the influence of carbonyl or carboxyl molecules, the carbon bonds connected are weakened and broken accordingly, thus destroying the aromatic ring and generating new active sites to enhance the reaction activity of coal. After CO2 activation at 800 ℃ or water vapor at 900 ℃, the number of active sites of semi-coke are increased by more than two times, respectively, and the proportions of carbonyl and carboxyl groups each increase from 18% to 32% and 34%. However, aliphatic carbons bonded to oxygen increase from 0.02 to 0.11 due to moderate CO2 activation, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.01 after steam activation, which is significantly lower than that of semi-coke after N2 pyrolysis. The mesophilic activation reaction of pulverized coal mainly forms more active sites through the formation of carbonyl and carboxyl group to destroys the aromatic structure. However, the products formed by the two groups are different due to their different scopes and rate-determining steps. CO2 mainly plays the activation effect by transforming the sp2 structure of coke edge into  the carbon structure rich in sp3 hybridization, while water vapor can be activated by inhibiting the graphitization process in the layer.