Abstract: Diamond/copper composites,on which diamond film was deposited as the insulating layer,were prepared by high temperature and high pressure（HTHP） sintering method,for the require ments of high thermal conductivity and insulation by power semiconductor devices.The results indicate that a high thermal conductivity value of 580 W/m·K could be achieved when diamond particle diameter is 80～120 μm and diamond volume percent is 80%.Part of diamond skeleton is formed as effective thermal channels under HTHP（6 GPa,1 200 ℃）.