In order to study the calculation of composite anchor force of anchor rod and the influence of anchoring angle on the surface shear force of anchored structures under the condition that the shear direction and the anchor rod tend to be coplanar, FLAC3D finite element software was used for numerical simulation. Firstly, the numerical calculation models were established based on the solid elements and contact surface elements, as well as the parameters needed in the numerical simulation process were inverted through the physical experiment results. Secondly, fish language in FLAC3D was utilized to record the variation of shear force of structural plane with the increase of shear displacement during shearing. Finally, according to the geometric relationship in the mechanical model, the distribution function of the reaction force of the compressive side along the anchor rod was obtained. On the basis of the classical beam theory, the mechanical model was established, and the shear force calculation formula of the anchor rod at the structural surface was derived using the principle of minimum potential energy and the displacement variational method. Through the numerical simulation tests, the results demonstrate that the shear force on the anchorage structure surface first increases and then decreases with the increase of the anchoring angle. When the anchoring angle β≤90°, the "guide rail effect" of the anchor rod is more significant; When the anchoring angle β>90°, after shear deformation, the rocks are separated due to the deformation of the anchor rods.