Abstract: According to the problem of large diameter and long-distance gas drainage drilling borehole failure with hole collapse and sticking in soft and breaking coal mass, the theoretical analysis, field test and underground test were used in this paper, the structural integrity and strength of coal mass were obtained by in-situ strength and structural test. Based on the results, the grouting mechanism of soft coal bonding, soft coal integrity and strength enhancing were proposed, the grouting parameters and full-length piecewise grouting technique were designed, this process was simple and fast. It is tested underground that the coal mass strength was increased by 57% and the integrity increased by 58.8%.