Abstract: The mathematical model of gas emission of coal particles was established according to Darcy law, the gas flow equations were simplified by dimensionless, and the finite difference method was used in the program for calculation. The number of condition substitutions in calculating process was reduced and some dimensionless quantities were got. The change rule of the gas pressure and the cumulative desorption amount in the coal particles was obtained from the analysis. Therefore, the introduction of the dimensionless quantity can simplify the solution process of the equations and the writing of the program, and the gas emission laws of coal particles which were got from it are more universal.