The mixed powder of W-40Cu ball-milled for different time was cold-pressed into a compact, then it was hot-extruded into W-40Cu composite. The effects of the mechanical ball milling on the microstructure and the performance of the composite were investigated. The results show that ball milling for long time has unbenefical effect on the microstructure and the performance of the composite. With prolonging of ball milling, the inhomogeneity of tungsten phase size within the composite appears obviously, the density and specific conductance of the composite decrease, and the hardness increases.