Abstract：Coal-rock electrical properties are very important，which reflect coal inner structure and ingredients，and vary obviously when coal is pressed or destroyed. In the paper，the alternative characters of current electric conduction of rock-coal porous medium with gas are studied. It is concluded that the conductivity increases along with gas pressure，and conductivity of coal without gas is smaller than that of coal with gas，the conductivity increases along with temperature whether the coal contains gas or not，and the conductivity of coal with gas is bigger than that of coal without gas under same conditions. The conductivity is not variated with the voltage of alternative electric field. The conductivity increases along with the frequency of alternative electric field，and the relationship between conductivity and the frequency is fractal one. It is possible that coal and gas outburst can be predicted by monitoring the variation of coal conductivity along with the gas pressure or coal temperature.
