The laser cladding of W-Cu composite powders is conducted by the coaxial powder feeding method and the influences of different process parameters on the geometrical characteristics and the particle distributions of single-track cladding layers are investigated. A concept of effective mass energy density (k) is also proposed. The results show that, in the experimental fabrication system with single-track cladding, the dissipation energy density of cladding layers is approximatively 3.5×10-3 kJ·mm-2. Under the certain fabrication conditions, there exists a critical value k′ of effective mass energy density in cladding layers. A dilution zone can be formed in the cladding layers when k＞k′. With the decrease of k, as for the W particles in cladding layers, the successive change from agglomerate to uniform distribution, distribution along the edge of cladding layer, and W-rim/Cu core structure occurs. For a single track multi-layer cladding, the value of k is significantly affected by the shape of the single-track cladding layer. The smaller the width-height ratio of cladding layer is, the smaller the actual k value and the relative density are.