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Diamond/copper composites possess excellent thermal physical properties, and its near-net-shape preparation can be successfully realized by means of melt in- filtration. The relevant process and the influencing factors of porous diamond preforms infiltrated by copper were studied. Research results showed that, it is advantageous for the infiltration process in condition that the copper blocks were placed at both the top and the bottom of porous preforms. Composite density could reach 99.3% which was near to full density, meanwhile the thermal conductivity could reach 628 W m-1 K-1, when the melt infiltration was carried out at 1230°C with the pressure of 20 MPa for 30 min. The density was not obviously increased by further improving the infiltration temperature and extending the heat holding time, however the thermal conductivity dropped, which was associated with the variation of interfacial thermal resistance due to the change of interface structure. There was an incubation period in the infiltration process, which brought that the composite density was lower and even that the infiltration cannot be completed, when infiltration temperature was below 1130°C or pressure was less than 20 MPa. [ABSTRACT FROM AUTHOR]