Abstract: According to the reaming requirement for large diameter directional drilling in hard rock of coal mine roof, the drilling technology of torsional impact rotary reaming is put forward. Based on the simulation results of FLUENT finite element software, the research of small displacement quantification transformation of torsion impactor is carried out, and the working performance of torsion impactor is tested. The relationship of throttle pressure drop, impact torque, throttle nozzle diameter and work displacement is verified. It is proved that the small displacement quantification transformation of torsion impactor can be realized by reducing the throttle nozzle diameter. The combination of rotary reaming tools with torsional impact is designed. The influence factors and calculation methods of reaming parameters such as drilling pressure, pump volume and rotational speed are discussed, and the matching of reaming parameters is improved. On this basis, the field test of rotary reaming drilling with torsional impact is carried out. The test results show that the mechanical drilling efficiency of primary reaming of ?准200 mm drilling hole is up to 10 m/h, which provides the technical basis for efficient reaming of large diameter directional drilling of hard rock in coal mine roof.