Abstract: In view of the inclined bolt of mine roadway under deep high horizontal stress bearing the combined load dominated by bending and tension, it is prone to fracture failure and leads to a local instability of roadway. Taking the lower roadway of No.2424 working face in the Suncun Coal Mine of Shandong Energy Group as the engineering background, the fracture characteristics of inclined bolt were investigated and analyzed. Therefore, the fracture characteristics of inclined bolt were obtained, the distribution of internal force and internal torque, the location of fracture dangerous section and the expression of equivalent stress were deduced, the fracture mechanics criterion with the maximum equivalent stress of dangerous section as the index was established, and the influence law of different anchoring parameters and lateral pressure coefficient on the maximum equivalent stress was revealed. The maximum equivalent stress increases with the increase of lateral pressure coefficient, anchorage length and preload torque, and decreases first, then increases and then decreases with the increase of bolt installation angle. Based on the study above, the Fish language built-in in the FLAC software was used to realize the characterization of the maximum equivalent stress of the dangerous section of the bolt, and the risk coefficient index K represented by the ratio of the maximum equivalent stress of the dangerous section to the allowable stress was defined. Based on this index, the determination method of strengthening support timing was proposed, and the deformation and failure law of surrounding rock under different strengthening support timings was obtained. With the increase of the risk coefficient K when strengthening the support, the maximum equivalent stress of the dangerous section of the bolt, the overall deformation of the surrounding rock and the concentrated stress first decrease and then increase. When the risk coefficient K is small, the elastic energy accumulation of the shallow surrounding rock is large, and the self-bearing capacity is insufficient. When the risk factor K is too large, the surrounding rock deformation is large, the damage is serious, and the overall stability is poor. Therefore, it is determined that the optimal and reasonable strengthen support timing is the risk factor K taking 0.8. The practice of strengthen support in the lower roadway of No.2424 working face shows that when the risk coefficient is 0.8(60 m ahead of the working face),the fracture rate of bolt is reduced by 87.9%,the deformation of surrounding rock is effectively controlled, and the stability of roadway is obviously improved.