Abstract: The W-coating was deposited on diamond surface by physical vapor deposition, then the diamond/Cu composites were prepared by spark plasma sintering（SPS）. The effect of coating time on the thermal conductivity of the composites was studied. The results show that, with the increase of coating time, the area covered by W element on diamond surface increases gradually. Meanwhile, the density of composites increases gradually, and the thermal conductivity increases first and then decreases. When the coating time is 30 min, the density and thermal conductivity of the composite reach 91.3%and 327 W/（m·K）, respectively.