This paper aims to study the effect of the interior bonding section length on axial force of prestressed anchor rod and its supporting effect on surrounding rock. In this study, the ratio of interior bonding section length to total length of anchor rod is defined as interior bonding section length coefficient. Based on the equation of the shear stress of anchorage interface, an expression is deduced, which describes the relationship between the axial force and total extensional length of anchor rod. Then the effect of the interior bonding length coefficient on axial force of prestressed anchor rod is analyzed, and it is found that axial force of anchor rod increases with decreasing the interior bonding section length. According to the combined arch theory of prestressed anchorage, the influence of the interior bonding length of prestressed anchor rod and its supporting effect are studied by using the FLAC3D numerical software. The results show that the decrease of the interior bonding section length is beneficial to enlarging the influence scope of prestress field, increasing the thickness of the ‘effective load-bearing ring’ and minimizing the depth of plastic zone and deformation of the surrounding rock. Finally, changing interior bonding section length is significant to coordinate the support the stiffness of supporting structure in engineering.