The dendrite misorientation is a typical defect in single crystal Ni-based superalloy castings. To date, there is still no explicit viewpoint on its generation mechanism. In order to trace the growth of dendrites, 30 layers of continuous slices were cut from a single crystal casting. The result shows that the growth direction of dendrite will continuously change during the solidification. A multicomponent phase-field simulation model was established to simulate the influence of solute convection on dendrite misorientation. The simulation result shows that, due to the existence of solute convection, the unstable distribution of solute can lead to the inhomogeneous driving force distribution at the tip of the dendrite, resulting in the orientation misorientation defect.