Abstract: Base on Hancheng Mine coal samples,Weibei coalfield was elaborated by means of mercury porosimetry combined with small angle X-ray scattering (SAXS) based upon the fractal theory.The results show that the variation characteristics of pore structure and pore heterogeneity of tectonically deformed coals (TDC) can be represented by the fractal dimension D.Strong deformed coals have higher fractal dimension D_Hg,higher heterogeneity and more complicated pore structure/surface,and lower permeability,indicating that the complicated pore structure resulted from strong tectonic deformation contributes to low permeable coalbed methane reservoir.With the stress strengthening,fractal dimension D_SAXS shows an increasing trend,suggesting that tectonic deformation leads to the complication of pore surface structure.Thus,the fractal dimension can be used as an indicator of the deformation degree of pore structure.