To study the difference of pore structure morphology and permeability before and after loading of different coal samples under certain loading conditions. The pore size of coal samples before loading was tested by mercury intrusion method. According to the results of mercury intrusion test adsorption pores (<100 nm) accounted for more than 60% of the total pores. scanning electron microscopy (sem), transmission electron microscopy (tem) and nuclear magnetic resonance (nmr) techniques were used to compare and analyze the fracture morphology and permeability of different coal samples before and after loading. the experimental results revealed that the compact structure of the coal sample was destroyed after loading, a large number of cracks were formed, and the original pores were further connected, and a large number of shear cracks were obviously observed. nmr measurements revealed that the total area of the t2 spectrum for parallel bedding of saturated coal sample before loading was 12692 (dimensionless) and that it increased to 46735, after loading. the vertical bedding before loading was 12295 and that it increased to 37623, after loading. the permeability of the coal body was significantly increased, and the same loading mode, the permeability of the parallel bedding after loading was larger than that of the vertical bedding. citation:liu, j, gao, j, jia, g and yang, m, 2019. study on microstructure differences of coal samples before and after loading, in proceedings australian mine ventilation conference 2019, pp 118132 (the australasian institute of mining and metallurgy: melbourne).>