Abstract: In this experiment, the effects of metamorphic degree, water content and particle size on the gas discharge rate of coal samples were studied by single factor experiment. Then the orthogonal test and variance analysis were used to study the significance of the influence of three factors on the gas discharge rate of coal samples. The test results show that the gas emission rate of coal increases with the degree of metamorphism of coal sample, decreases with the increase of water content of coal sample, and increases with the decrease of particle size. The gas discharge rate is approximately logarithmically related to the degree of coal sample metamorphism, and is approximately quadratic with the immersion time, and is approximately a power function relationship with the particle size. The orthogonal test data is analyzed by variance analysis to obtain three factors for coal sample gas. The degree of influence of the release rate from large to small is: degree of deterioration, water content and particle size.