Abstract: Focusing on the failures to reveal core issue of the correlation of coal structure and reactivity based on the method of physical similarity of traditional coal chemistry in the past 170 years,and the modern analytical instruments and quantum chemical calculation of coal macromolecular structure in the last 70 years,a solubility systems for coals was developed based on a step-wise solvent extraction method with cyclohexanone followed by CS2-NMP for the first time.The concept of relative extraction yield was also proposed.According to the chemical similarity,the organic matter in coal was divided into saturates,aromatics,colloid,asphaltene,carbene and carboid.Physical and chemical structures,and composition,as well as pyrolysis behavior,pyrolysis properties,reaction mechanism and dynamics research for the groups at different metamorphic degree of coals were systematically investigated.The new ideas of radical coal pyrolysis reaction principal dominated by the thermal dissociation of radical dominated pyrolysis were proposed and the regulation mechanism of free radical and its strengthening mechanism were formulated,which can be used to explain the phenomenon of coal plasma pyrolysis of acetylene in the reaction process and mechanism,and why the product acetylene selectivity is as high as 80%,and also to interpret the tar yield maximization and other industrial phenomenon during low rank coal fast pyrolysis.Thus the study has developed the modern coal chemical research method based on chemical group compositions,realizing the coal molecular identification,the characterization and description of the coal composition,the parameters of coal physical and chemical structure,the presence of various chemical bonds and the harmful composition in coals.Therefore,taking advantage of the coal chemical group composition,from molecular level,the reaction mechanism of coal conversion process,reaction mechanism and reaction kinetics were investigated to reveal the various coal similarities in terms of reactivity.The study will improve the efficiency of the coal conversion process,reduce the pollution emission,and provide a theoretical basis for a high clean conversion of coal resources and utilization.