Dislocation movement is closely related to the plastic deformation behavior of crystals, and the reaction between lattice slip dislocations and grain boundaries plays an important role in the plastic deformation of polycrystalline materials. In this paper, starting from the microstructure, the slip motion of $1/2\left[ {\bar 110} \right]\left\{ {111} \right\}$ mixed dislocation in rock salt structure TiC single crystal was studied by molecular dynamics (MD) method, and the interaction between the mixed dislocation and the sub-grain boundary composed of edge dislocation array with slip system was simulated. The $1/2\left[ {\bar 101} \right]\left\{ {1\bar 11} \right\}$ results show that the mixed dislocation with slip system $1/2\left[ {\bar 110} \right]\left\{ {111} \right\}$ has a wide dislocation core structure. When a single slip mixed dislocation is merged into the inclined boundary array, there are steps and extended dislocation nodes on the steps. When the incident dislocation line intersects with the grain boundary plane, the intersection of the incident dislocation line and the grain boundary dislocation line hinders the dislocation movement. The step related to the node is in the {111} plane and it will dissociate into partial dislocations, resulting in a surface defect with a habitual plane of {111}.