Abstract: The first coalification jump significantly changes the physical properties of coal reservoirs in the early stage of coalification. In view of this dynamic change characteristic of physical properties and in order to determine the evaluation parameters and standards of the favorable low-rank coal reservoirs before and after the jump of coalification, the material composition, pore-fracture system and reservoir physical properties of low-rank coal reservoirs in the early stage of coalification were studied by means of a series of experimental analysis methods on the basis of systematically collecting low-rank coal samples from major basins in China. In the early stage of coalification, the changes of pore types are mainly characterized by the destruction and contraction of primary pores, and the formation of secondary thermogenic pores and cleats. The reservoir space is mainly distributed by macropores and mesopores, and gradually changed to pores and fractures. From lignite to low-rank bituminous coal, with the progress of coalification, the porosity of coal reservoir shows a trend of first decreasing rapidly and then increasing slowly, and the overall permeability shows a trend of increase. The adsorption capacity of methane and the proportion of adsorbed gas increases gradually. Based on the detailed description of the pore type, pore size distribution, porosity, permeability and gas occurrence mode of the low-rank coal reservoir before and after the first coalification jump, this paper proposes the differential treatment method for the weight and membership degree of evaluation parameters between lignite and low-rank bituminous coal reservoir, aiming to provide a scientific basis for the exploration and development of low-rank coalbed methane in China.