Abstract: In order to research the best ratio of the cement grouting in the process of the coal seam gas pressure measurement, we measure the basic properties of slurry, research drainage rate, rate of stone, final set hardening time under different water cement ratios, sodium silicate, simulate hole sealing condition of cement mortar in coal seam pressure measurement, design the drilling of 12 m in length and 75 mm in diameter, carry out hole sealing experiment of cement mortar under the conditions of different ratios of grouting by changing the angle of drilling. Slitting the drilling and observing it, measuring the effective length of stone and the permeability of stone, acquiring cement sample piece of stone simulated in drilling under the different ratios, the best ratio of the cement grouting in cement mortar sealing is given at last.