Abstract: To improve the relative density of sintering billets made of mechanically milled composite powders,3%C-Cu composites have been prepared by hot extrusion.Effect of milling time,extrusion temperature and extrusion ratio on extrusion pressure and the relative density of 3%C-Cu composites was investigated.The microstructure was also analyzed by field emission scanning electron microscopy.The results show that extrusion pressure increase when mechanical milling time of powders was prolonged or extrusion temperature was powered.The relative density of composites increase with extrusion ratio and the latter is the main influencing factor for the former.At the same extrusion ratio,composites with the best densification can be achieved by sintering billets prepared by 3 h-milled powders at 750 ℃.No diffusion occurs between copper and graphite within composites.