Three kinds of coal samples with different components are chosen as study objects.Density calculation and SEM are adopted to study their internal structures,and a selfmade triaxial gas seepage instrument is used to study their internal gas flow characteristics.The results show that internal structures of coal samples made of different particle size coal powders under identical external conditions are various,and nonlinearity is presented on the influence caused by fabric.Gas flow characteristic is complex in complete stressstrain process,generally it firstly increases and then decreases,initial gas flow velocity is lower than the one after the failure of coal sample,and obvious hysteretic nature of gas flow characteristic is showed.The influence of gas flow characteristic caused by initialinternal structure of coal sample is nonlinear and the stresssensitivity is high on the influence of gas flow characteristic caused by initialinternal structure.The more complex the initialinternal structure of the coal sample is,the lower the axial tresssensitivity is,and the higher the confining pressuresensitivity is.