During the formation of a three-dimensional (3D) point cloud of parts using the monocular grating projection system, the reflections of the surfaces and boundaries of parts cause the mutation of part point clouds, making errors in the subsequent reconstruction and measurement process. In this paper, a phase compensation method is proposed. An image-processing algorithm is designed by combining the contour information of the object and the increasing characteristics of the phase-level graph to compensate for the continuous phase graph and reduce the interference caused by the reflections on the surfaces and boundaries of the parts. The experimental results show that phase compensation can reduce the number of point cloud mutations on the surface and boundary of parts. In addition, phase compensation can improve the reconstruction effect of the 3D point cloud in the case of reflections on the surfaces and boundaries of parts.