To solve the problem of grout-rock interface relaxation due to self-shrinkage of cement-based material grouting in deep fractured rock masses, a bolt-grouting reinforcement method for deep fractured rock masses based on prestressed anchor and self-stress grouting was proposed. A self-stressed grouting reinforcement model and a new prestressed anchor rod–grouting reinforcement model for a single fractured rock mass were established. The mechanical characteristics of fractured sandstone specimens with ordinary and new bolt-grouting reinforcement were studied in physical experiments. The effectiveness of the new prestressed anchor rod-grouting reinforced rock mass was verified in engineering applications. Results showed that within a certain range, the greater the expansion restraint stress of the slurry stone is, the stronger the reinforcement effect on the fractured rock mass is. The expansion restraint stress of the slurry stone and the axial stress of bolt both contributed to the increase of the maximum principal stress of the fractured rock mass. The peak strength of the new prestressed anchor rod–grouting reinforced sandstone was 10% higher than that of the anchor rod-grouting reinforced sandstone. Its peak strain was slightly lower than that of the anchor rod-grouting reinforced sandstone. Moreover, the elastic deformation stage of the new prestressed anchor–grouting reinforced sandstone was shortened, and its reinforcement effect was enhanced. The surrounding rock of the substation roadway, which could not be well controlled by anchor-net support, U36 steel support or anchor rod-grouting reinforcement, was effectively controlled by new prestressed anchor rod–grouting reinforcement, and the maximum displacement of the surrounding rock on the roadway surface was 83 mm.