Abstract: Coal firmness coefficient f and initial velocity of gas diffusion△p reflect the major indexes of the coal and gas outburst. Permeability reflects the difficulty of coal seam gas extraction. In some ways, the coal structure determines the f, △p and permeability. How to identify the f, △p and permeability of coal quickly, and the prediction of coal and gas outburst and drainage service has become the focus of attention. To this end, through the coal wall observation in the underground coal mine, we obtain a quantitative characterization parameters of coal structure that is the geological strength index GSI, and establish the quantitative relation of GSI and f, △p, permeability. That is to say, through direct observation of GSI for estimating the three parameters, which is contribute to obtain three parameters more efficient and convenient, so as to guide production at any time. The results show that the f increases with the increase of GSI, and presents a positive linear correlation; △p decreases with the increase of GSI, and presents a negative linear correlation, and the relationship between permeability and GSI is a normal distribution, which peaked at GSI=52.7. In addition, when coal is wet,f increased, while △p decreased, but they still remain the dried coal sample similar linear relationship with GSI.