Abstract: Locking bolts are frequently used to control the failure of the supporting arch in soft rock roadway support system, but the design basis of the locking bolts parameters is not clear. In order to investigate the roadway support effect influenced by the position and length of the arch-locking bolt, based on a typical soft rock roadway engineering case, numerical simulation experiments were carried out through an improved numerical simulation approach. The results indicate that: roadway supported without locking bolts deformed seriously, and the arch legs’ inward bending deformation and arch-rock separation were the breakthrough of the overall failure of the support system; the arch-locking bolts suppressed the arch legs inward bending deformation and prevented arch-rock separation, which ensured the integrity of the support system, and the final supporting effect was improved significantly; the deformation value and plastic zone volume both first decrease and then increase with the increasing of the locking bolt height H, and the impact was significant; the support effect tends to be better but not obvious with the increasing the arch-locking bolt length L. Based on the research conclusions, the optimized parameters of the lock arch bolt (H=1.0 m, L=3.0 m) were determined, and the field practice showed the optimization scheme works well.