Abstract: The tungsten-coated diamond/copper composites were simulated by the finite element analysis software ANSYS in this paper. The effects of diamond volume fraction, diamond particle size, and tungsten coating thickness on the thermal conductivity and thermal expansion coefficient of the diamond/copper composites were investigated. The results show that, the thermal conductivity of the composites increases as the increase of the diamond volume fraction and diamond particle size and as the decrease in the coating thickness of tungsten. The thermal expansion coefficient is mainly controlled by the volume fraction of diamond. The simulation results fit the literature data very well. The simulation results also indicate that the diamond particle size in 150~200 μm is optimal.