Abstract: A airtight large-diameter urn was made in which electromagnetic radiation (EMR) antennae can be placed and the experimental system was set up that can detect EMR signals during gas flowing in coal. EMR spectrum analysis was done by Fourier transform when different kinds of gas under different pressure gradients flow in coal. The results show that frequency band of EMR produced by gas flowing is usually in low frequency and its main frequency band increases with the increase of pressure gradient. The higher the pressure gradient and the rate of gas flow, the more intensive the destruction of coal and the motion-electricity effect, and the higher the frequency of crack oscillation.