In the numerical simulation for cooling channels of aircraft electric machine, the mesh has a crucial impact on computational accuracy and computational resources. A comparative analysis is conducted on the applications of Tetrahedral, Hexahedral, and Mosaic mesh in the numerical simulation of cooling channel. The effects of boundary layer number and cell size on element number and computational results are summarized, and the impact of element number on computational results is compared. The results showed that when the cell size or boundary layer number is the same, the Mosaic mesh has fewer elements and lower resource occupancy. The Mosaic mesh achieves the same computational results with fewer elements and is easier to converge.