High power diode laser (HPDL) is advanced portable equipment with the high value electrical to optical conversion efficiency. Diode lasers have seen wide applications in material fabrication and processing. Aggregate WC-Ni based superhard composites were fabricated on 304 stainless steel substrate. Wear-resistant coatings were fabricated by a 3 kW diode laser with direct injection powders into the molten pool. The coating had excellent bonding with the substrate and was free of pores and cracks. The morphology of laser cladding layer was observed by scanning electronics microscope (SEM),composition analysis was applied by energy dispersive spectroscopy (EDS),and the phase transformation was characterized by X-ray diffraction (XRD). The results showed that WC-Ni based superhard composites was fabricated by high power diode laser with high content tungsten carbide (60%) and low dilution. The main structure of diode laser cladding WC-Ni based alloy was γ-Ni,WC,W2C,Ni3B,CrB2 etc. The hardness of the laser clad layer is inhomogeneously distributed with the average value of HV 1100,higher than the substrate of HV 350. The hardness in the transition region is gradient distributed with steep reduction.