Abstract: Abstract A series of PCD (polycrystalline diamond) samples with Si binder are produced at various high temperatures (1100℃一1650℃)and ultrahigh pressures (4.5-6.25GPa).Their structures and wear resistance are investigated by x-ray diffraction analysis, SEM observation and abrasion test.The resin is are shown that there are three zones on the P-T graph corresponding to various PCD structure.G-ratio of PCD which consists of diamond and SiC is optimum.Si is retained at lower pressure and lower temperature and diamond graphitization occurs st lower pressure and higher temperature.Thus,the wear resistance of these PCD is lower.The pressure and temperature conditions far PCD consisting of diamond and SiC are discussed.