Abstract: The efficient decarbonization and quality improvement of coal-series kaolin is the premise and guarantee for subsequent deep processing and utilization. The influence of mechanical modification on the surface elemental composition, functional groups, and charging performance of different component particles(kaolinite and clean coal) in coal-series kaolin was studied by Fourier transform infrared spectrum(FTIR),X-ray photoelectron spectroscopy(XPS),and charge-to-mass ratio tests. The effect of mechanical modification on the decarbonization performance of coal-series kaolin was also investigated using rotary triboelectric separation tests. The research results show that the mechanical modification could change the elements and functional groups on the surface of kaolinite and clean coal particles, which caused the changes in the surface charge properties of kaolinite and clean coal particles. The mechanical modification resulted in an increase in the content of C—C groups, a decrease in the content of C—O groups, and an increase in the content of C=O groups or —COOH groups for the surface of kaolinite and clean coal particles, which enhanced the tribo-charge performance of kaolinite and clean coal particles. After the mechanical modification, the decrease in the content of Al and Si elements on the surface of kaolinite increased its negative charge; the increase in the content of C,Al and Si elements and the decrease in content of O element on the surface of clean coal increased its positive charge. With the increase of mechanical modification time, the charge-to-mass ratios on the surface of kaolinite and clean coal particles showed a trend of first decreasing and then stabilizing. When the mechanical modification time was 40 s, the kaolinite and clean coal particles had strong charge ability, i.e.,the charge-to-mass ratio of 0.074-0.125 mm and 0.125-0.250 mm clean coal was 12.88 nC/g and 13.16 nC/g, respectively, and that of kaolinite was-5.41 nC/g. The difference in charge-to-mass ratios between kaolinite and clean coal was large and stable, which was conducive to promoting the decarbonization performance of coal-series kaolin via triboelectric separation. Under the optimum test condition, after the mechanical modification, the decarbonization efficiencies of 0.074-0.125 mm and 0.125-0.250 mm coal-series kaolin were 41.35% and 37.17%,their concentrate yields were 72.92% and 77.05%,and their valuable component recoveries reached 82.27% and 83.99%,respectively, which achieved an efficient decarbonization and pre-enrichment of coal-series kaolin.