Abstract: To clarify the influence rule of electrolyte concentration on the physical properties of coal-bearing mudstone in electrochemical modification test，taking coal-bearing mudstone from the Cenozoic coal measure strata as a sample，the electrochemical modification test was carried out by using a self-developed percolation electrochemical modification test device for soft rock， and the variation rules of free expansion，water absorption and mechanical strength of mudstone specimens under different electrolyte concentration were studied. Results show that the swelling rate and water absorption of mudstone specimens decrease with the increase of electrolyte concentration；the surface integrity of mudstone specimens increases to a certain extent with the increase of electrolyte concentration，and the resistivity of mudstone specimens decreases；the concentration of electrolyte and the uniaxial tensile strength of the specimens show a certain range. Degree is positively correlated.