The microstructure and mechanical properties of pure copper clad Aluminum wires in different diameters by drawing at room temperature were studied in this paper. The results show that the microstructure of the cladding wire by drawing at room temperature is vimineous grain as fibril shape from prime equiaxed grain. The fibril diameter is in inverse proportion to deformation and the fibril length is in direct proportion to square of deformation approximately. The ultimate tensile strength of the cladding wire by drawing at room temperature increases in direct proportion to square root of deformation, and the elongation decreases and fluctuates. Basis of the ultimate tensile strength of prime pure copper and aluminum alloy, the ultimate tensile strength of the cladding wires in different diameters can be doped out by mixed principle of composite material.