The process planning of a manufacturing method is the key to ensure the quality of the fabricated part. In Additive Manufacturing (AM), slicing is a crucial step in process planning to convert a Computer-Aided Design (CAD) model to a machine-specific format. If the slicing results were incorrect, the manufacturing quality would have no way to be assured. Therefore, it is important to understand the performance of different slicing technologies for AM. Digital Light Processing (DLP) printing is an important AM process that has a good surface finish, high accuracy and fabrication speed, and is widely applied in many dental and engineering industries. However, while most other AM processes are toolpath-based, as a process that uses images as the fabrication tool, the DLP printing has its process planning understudied. Therefore, the main goal of this paper is to study, compare and benchmark the slicing technologies for DLP printing. Three slicing technologies are compared: contour, voxelization, and ray-tracing. They are tested with some common defects in slicing, and their usage in computational resources is also reported. The summary and suggestion are given at the end.