Abstract: The sampling depth is different under the condition of different drilling tools and coal seam occurrence.To ensure the reliability and accuracy of gas content measurement and provide the basis for arrangement of working face,this paper studied the reasonable sampling depth of working face.The maximum sampling depth of reverse circulation sampling device by simulation sample test is obtained.Through taking 12033 working face of a mine in Guizhou as an example,by using SDQ-63 deep hole fixed-point sampling device,reasonable sampling depth is determined by site inspection that the up-hole is 110 m and downward drilling hole is 94 m.