The experiments of laser-clad nickel-based alloy powder doped with (MoO3+B2O3) were carried out on steel A3 substrate. The microstructural and metallographic analyses were performed by a scanning electron microscopy, energy-dispersive spectrometer and X-ray diffractometer. Effect of content of (MoO3+B2O3)-doping on the cracking susceptibility and the microstructure of Ni-based composite coatings has been analysed. The hardness and wear-resistance of the coatings were also studied. It is shown that good finish and crack- and porosity-free coatings can be achieved under a proper amount of (MoO3+B2O3)-doping and a suitable processing technique, and that a strong metallurgical bonding is presented between the coating and the substrate. Both the cracking sensitivity and the wear resistance are considerably improved at the little expense of a decrease in hardness. This can be attributed to the refinement of the microstructure both in grain sizes and their homogeneous distribution in the coatings. The microstructural and metallographic analyses suggest the composite coating consists of the eutectic composed of BMo2C, Cr23C6 and Ni4B3 dispersed in the γ(Cr-Ni-Fe-C) matrix. Thus, it can be concluded that the refinement in microstructure is due to both an increase in number of nucleation sites by the formation of BMo2C in the melting pool and an impediment to the growth of larger brittleness phase CrB by the (MoO3+B2O3)-doping.