Abstract: Taking the low coal rank coal reservoir of Huolinhe Basin in Erlian Basin Group as the research object，the typical section in the open pit coal mine is dissected by examples，supplemented by optical microscope，CT scanning and other laboratory test and analysis methods to describe the coal in the study area in detail Reservoir fissure system development characteristics，build a vertical space fracture development model of the target coal reservoir，and provide reference for subsequent engineering development. The results of the study show that the coal reservoir large-fracture system and micro-fractures in the Huolinhe Basin show good orientation，the exogenous joint dip angle is almost upright，and the endogenous fissures and micro-fissures are mostly developed perpendicular to the plane. The micro-fissures are mainly primary tensile fissures，and there are no shear fissures with structural features. The extent and direction of the development of exogenous joints and the morphological characteristics of endogenous fissures are obviously affected by the structure，but the degree of micro-fissure development is mainly affected by the composition of coal and rock，but not by the structure. Large-fractured systems are rarely filled，and micro-fractured filling is relatively large，about 40% to 50%，and overall reservoir connectivity is better. The CT three-dimensional reconstruction imaging of coal shows that the voids filled with inorganic minerals and unfilled voids have the characteristics of stratified distribution，and the overall pore cracks are developed. The inorganic minerals filled in the Ⅳ coal group are less than those in the IIIA coal.