To study the conductivity changing rules of low-rank coal reservoir during methane absorption and desorption, this paper, based on a case study on No.4 coal seam in Binchang coal mine, measures the resistivity of different coal samples during methane absorption and desorption, studies the conductivity changing rules and mechanism, and compares their variance of different coal rocks. Conductivity rises during the absorption process with an ascending pressure. Relation among resistivity, absorption quantity and equilibrium pressure can be described as a quadratic function. During pressure-descending-desorption process, conductivity rises slightly; it has linear relation with absorption quantity and equilibrium pressure. Heat-releasing and coal matrix swelling make a rise in conductivity during methane absorption, and vice versa. Methane absorption results in an irreversible change in coal structure; its resistivity cannot be recovered to its original level even after methane desorption. Durain, with high ash, even pore throat structure and less charged particles, is weaker than vitrain in conductivity, but stronger in absorption, leading to a greater and faster decrease in conductivity during methane absorption.