Abstract: In view of the possible hydraulic connection between Huachi Formation and Luohe Formation aquifers in Binchang Mining area, uneven water richness in Huachi Formation aquifers, unclear porosity and permeability characteristics of salt-soluble mudstone in Huachi Formation, and huge water inflow in the mine roof aquifer, we selected the core of Huachi Formation at different vertical depths in Binchang Mining Area, and adopted porosity and permeability testing, nuclear magnetic resonance and other methods to study the microstructure characteristics of aquifer in Huachi Formation comprehensively. The research results show that the sandstone permeability of Huachi Formation is the highest, and the corresponding porosity is also the largest, the permeability of salt-soluble mudstone is the second, mudstone has the lowest permeability; silty and fine sandstone have high permeability, which is conducive to groundwater runoff, paste and salt dissolved pore mudstone has very developed solution pores, but its permeability is very small, poor throat connectivity, strong heterogeneity of pore structure, poor dissolved pore connectivity, which is not conducive to groundwater runoff. The overall porosity and permeability of Huachi formation are positively correlated, and the permeability of the formation is mainly affected by the pore structure. The proportion of micropores in salt-soluble mudstone of Huachi Formation is the highest, reaching 50.03%; the proportion of large and medium pores of 0.1 μm to 10.0 μm in fine sandstone, silty sandstone and giant coarse sandstone is the highest, reaching 36.67% to 59.96%, and the proportion of micro-cracks is below 1%; the overall proportion of large pores in sandstone is relatively high, and micro-pores and small holes are the main types of salt-soluble porous mudstones, and sandstone pores provide a good channel for the occurrence and migration of groundwater, the pore development of salt-soluble mudstone is poor, the effective porosity and permeability of salt-dissolved mudstone are very low, the effective porosity is only 2.59%, the effective porosity of sandstones with different grain sizes is 11.74% to 20.38%, and the permeability is (75.38−3 552.00)×10⁻¹⁵ m².