Abstract: This paper analyzes the stability of large-diameter directional drilling, using the 40103 working face of Dafosi Coal Mine in Shaanxi Province as the engineering background. FLAC^3D is used to simulate the stress, displacement, and plastic deformation of the surrounding rock under different diameters. The effect of equivalent stress drilling protection is also analyzed. Axial compression experiments are conducted on drilling protection pipes with varying diameters and internal supports. Additionally, the impact of selecting diameter and horizon on drilling drainage effect is further verified through field practice of high-level directional drilling. The research results indicate that as the size of roof drillings increases from as 100 mm, 130 mm, 160 mm, and 200 mm, drilling stability decreases and the surrounding rock mass gradually becomes unstable and deforms. Therefore, it is recommended to select a Φ160 mm drilling on site. After simulating equivalent stress to protect the drilling, the stress concentration in the surrounding rock of the drilling is relieved, and the displacement and plastic failure zone of the surrounding rock mass are also reduced. Compared to the common drilling protection pipe（without internal support）, the drilling protection pipe with internal support structure significantly improves compressive performance. The effect of one-line and cross is better, and the compressive strength of the cross-drilling protection pipe is four times that of the common drilling protection pipe. The directional drilling drilling of the Φ160 mm has achieved effective drainage. During the mining process, from the cut to 315 m, the gas drainage flow rates are measured at the first horizon of the caving zone（13-15 m）, the second horizon of the caving zone（23-25 m）, and the third horizon of the fracture zone（33-36 m）, the gas extraction flow rates are 1.46-4.21 m³/min, 1.58-5.32 m³/min, and 1.53-6.02 m³/min, respectively.