Abstract: In order to study the influence of acidification on the permeability of coal reservoir,indoor acidification experiment was carried out. Coal samples with developed fractures in NO.3 coal seam of Jincheng area of Qinshui basin in Shanxi Province were adopted. The coal samples were made into dry pulverized coal of 60-80 mesh and coal cores of 50 mm in diameter, then the pulverized coal and coal cores were processed with different acids. The dissolution rate after acidification of the pulverized coal, the permeability and the porosity before and after acidification of the coal cores were measured. The results indicated that after acidification the permeability of the coal cores increased from about 0.5×10^-3 μm² to 3.0×10^-3μm² and the porosity increased about 5.5%. Acidification of coal core could greatly improve its permeability. The research results provide an experimental support for the application of coalbed methane acidification operation.