Abstract: By testing the gas diffusion velocity and volume of several coal samples using WT-1 constant volume and pressure swing device, combined with the mathematical model of coal gas emission, the characteristics of gas emission were obtained. The experimental results showed that the △p index would fail to declare. By using the least squares method to fit the different mathematical formula for gas emission, the results show that Venter type is more suitable for formula of diffusion velocity within 1 min, and the greater the diffusion volume, the higher the relativity with Venter type.