Abstract: In the coal mass support with glass fiber reinforced plastic bolt, its anti-torsion performance compared with the traditional screw steel bolt is poor; oversize torque causes the failure of anchorage performance, so the relative torsional angle θ of unit axis length generated by FRP bolt deformation needs to be expressed by pre-tightening force. Based on the assumption that the glass fiber reinforced plastic anchor rod is considered as the state of the round rod, and the relationship and the variation trend of the torsional moment M and the axial length of glass fiber reinforced plastic anchor rod deformation are established. Results show that when FRP bolt applied torque 0 N·m to 45 N·m, M and θ can establish a relatively simple mathematical expressions; within a certain range, using torsional moment to predict and quantify the bolt torsion deformation can be used as a more accurate and easy construction judgment way.