In this paper, WC-12Co particles were deposited on aluminum, copper and stainless steel substrates by High Velocity Oxy-fuel (HVOF) process. Both the surface and the cross-sectional morphology of the two-phase semi-molten particles were observed and analyzed by Scanning electron microscopy (SEM). The collision model of the two-phase particles with matrix was simplified as the process interacting with substrate of liquid phase Co and solid phase WC, and an improved mathematical model was established to calculate the relative deformation ratio λ of the substrate to the splat. It was found that WC-Co particles deposited on aluminum, copper and stainless steel substrates exhibited hemispherical-like, pie-like and sputtering-like morphologies, respectively, and different shaped WC-Co particles had different λ values. Compared with forming hemispherical-like (λ>1) and sputtering-like particles (λ<1), moderate deformation occurred in both particles and substrates when pie-like (λ=1) particles were formed, which was beneficial for increasing the effective contact area between particle and substrate, thus improving the bond strength.