In this paper, a trajectory planning method for laser cladding of robot surface based on spot control technology is proposed. The energy density of laser input surface is controlled by the change threshold of spot projection area. The influence of defocus and attitude on the cladding quality is analyzed by changing the geometrical shape of laser beam projection spot on the surface trajectory interpolation point. The results show that the cladding effect is better when the defocusing amount is 5 mm, the cracks appear when the space angle is 23.4°; the inclusions and cavities appear when the space angle is more than 30°; the thickness of the cladding decreases with the increase of the space angle and the overall hardness is higher than that of the substrate. The trajectory interpolation points are verified by the change of spot area, and then the attitude change is controlled to achieve high-quality cladding on the laser surface.