Abstract: In this paper.the author uses the theory of fluid mechanics.dynamics of fluids in porous media,gas seepage flow in coal seams and combines the tests in the laboratory with the actual coal infusion to have an investigating and study from the theory to the mechanism of coal infusion to wet coal seams.Through the analysis to the process of coal infusion the author builds up the mathematical models and has a detailed discussion to the boundary conditions of coal infusion.Because the equation sets to describe coal infusion are non-linear.we have made a simplification to them to use the dimension analysis theory by leading into the non-dimensions of water pressure of coal infusion,seepage flow rate.increment of coal seam moisture and so on Besides the analytic and approximate solutions have also been discussed.At last.we use the scientific research item of the actual coal infusion to illustrate the effects and importance of the theory to direct actual coal infusion and its designs.