Cemented carbide is widely used in the mold industry due to its excellent wear resistance. However, due to the high hardness and yield strength of cemented carbide, it is easy to cause tool wear failure and difficult to guarantee surface quality. Milling-grinding combined machining with PCD micro mill can effectively improve machining quality and reduce tool wear. In this study, the mechanism of milling - grinding combined machining of cemented carbide is analyzed, and a PCD micro end mill structure with 0° circumferential relief angle is designed to realize the above mechanism. Then, according to the geometrical motion principle of the six-axis CNC machine tool, the multi-axis simultaneous grinding method and the mathematical model of the helix flute grinding trajectory are established to realize the fabrication of the new micro mill with certain helix flute width. Finally, comparison experiments of milling performance between the new micro mill and standard micro end mill are carried out, and the workpiece surface quality and the tool wear morphology are observed and analyzed. The results show that the surface quality and wear resistance of the new micro mill are improved compared to the standard end mill. It is validated that the PCD milling - grinding micro end mill can be used for high surface quality and high efficacy machining.