Abstract: To eliminate the influence of the cantilever beam roof on the stability of roadway by rotating extrusion and to determine the reasonable width of roadside supporting wall, the forming conditions of cantilever beam can be eradicated through deep hole blasting to pre-split and cut the roof below the side crack zone of goaf beside the roadway, which artificially causes the roadside supporting wall to bear only the weight of the overburden static balance rock block. In the calculation of this static model, the relationship between the supporting resistance of roadside support wall and the length of hanging roof below crack zone is studied, and the influence of side hanging roof on the damage of roadside support wall is analyzed. The relationship between the supporting resistance of roadside support wall and the height of crack zone after cutting roof by deep hole blasting is studied, and it is concluded that the extrusion failure of the roof on the side supporting wall of the roadway after cutting the roof is obviously reduced, and then the stability of the retaining roadway is maintained. The mechanical calculation equation of the width of the roadway supporting wall was derived, and the reasonable width range of the roadway supporting wall of C30 concrete material was calculated. The dynamic pressure coefficient of 1.2 was used to obtain the analytical solution of 1.5 m width of the roadway supporting wall under the condition of cutting the roof, and this parameter has been successfully applied in engineering practice. The results of the mine pressure observation in 3207 working face of Nanyang Coal Mine show that the roof of the roadway side mined-out area under the height of the caving zone is conducive to the stability of the retaining roadway, and the width of the supporting wall confirmed in this condition is reasonable and feasible.