Abstract: Aiming at the problems that the bolt can not be repeatedly pre tightened and the strength of the bolt is weakened after the wall expansion of Ji 15-23090 machine roadway in Pingdingshan No.4 coal mine, this paper puts forward a new type of pre tensioned bolt supporting equipment, and studies the influence of the pre tensioned force on the bolt anchoring performance. Through numerical simulation and uniaxial compression test, the characteristics of rock mass strength and internal fracture development under different pretensions are analyzed. The results show that: (1) the peak strength and residual strength of rock mass can be effectively improved and its ultimate bearing capacity can be enhanced by tensioning high pretension anchor（ 2) High preload can restrict the development of internal tension and shear fractures, and improve the integrity of rock mass. After the tunnel test, the bolt pretension is generally more than 60kn by tensioning the lock. After using the lock to fasten the bolt, the displacement of the roadway side is reduced by 44.3% compared with the original support method, which solves the problem that the bolt can not be repeatedly preloaded due to the insufficient length of the tail thread, and reduces the construction strength and support cost.