The important factors, as types of grid and grid quality, have effecting the numerical simulation of twin screw compressor. Based on domestic and international application，research status and grid quality evaluation criteria, firstly the principle of generating unstructured grid and structured grid in twin screw compressor is discussed. Besides, their respective advantages and disadvantages are given. The basic method to generate the rotor end surface and three-dimensional (3D) grid based on algebraic method generation as well as the problems that often appeared in the grid generation were emphasized in discussion. Finally, the generation of unstructured rotor grid based on Delaunay triangulation and structured rotor grid based on algebraic method were given. It provides a reference for meshing twin screw compressor rotor and selecting the rotor grid type.