Abstract: In order to study the influence law of the gas to the coal resistivity,a resistivity test system of the gas contained coal was established. The resistivity variation law of the coal samples from different mining area under the different gas pressure was tested and analyzed. The paper systematically stated the function mechanism of the gas pressure to the coal resistivity. The results showed that with the gas pressure increased,the coal resistivity would be in a declined trend. The resistivity and the gas pressure could meet the relationship y=a+bln(x+c).The correlation coefficient was high. In the initial period of the test,the resistivity would have a high decrease range and in the late period,the resistivity would have a low decrease range and then would be in stable. The gas would be affected to the coal resistivity and would be divided to three mechanisms of the thermodynamics,electrics and mechanics. The apparent resistivity of the gas contained coal would be the joint function results of the three mechanisms. The exothermic process of the coal adsorption,conductive energy barrier reduced and stress effect to the coal molecules all would cause the reduction of the gas contained coal.Among them,the stress effect to the coal molecules and the stress effect mechanism would be the leading mechanism.