Abstract: In order to solve the problems of surface forming and polishing of polycrystalline diamond (PCD), and improve PCD processing efficiency and surface quality, the PCD surface was machined by EDM coarse/fine discharge or diamond grinding wheel. The surface morphology, composition and microstructure of PCD were observed and analyzed by SEM, EDS, XRD and Raman spectroscopy. The microhardness and wear resistance of PCD in different processing modes were tested and analyzed. The influences of different processing methods and modes on microstructures and mechanical properties of PCD surface were investigated. Experimental results show that there are graphitizations on the PCD surface after EDM, but none on that after mechanical grinding. The microhardness and wear resistance of EDM precision machined PCD are 5 613 HV 10 and Q 5.8×10⁴while those of mechanically ground PCD are 5 727 HV 10 and Q 5.4×10⁴. There is limited difference between them. As with the EDM rough machining, the values are 4 604 HV 10 and Q 4.7×10⁴, respectively. The performance is significantly reduced.The concept of the surface metamorphic layer of PCD after discharge machining is proposed, the reasons of which are discussed.