The impacting droplet of a melting point much higher than substrate will result in the melting of the substrate around impact area. The melting of substrate surface to certain depth alters the flow direction of droplet fluid. The significant change of fluid flow direction leads to the detaching of fluid from contact with substrate. Consequently, splashing occurs during droplet spreading process. In the present study, Mo splats were formed on stainless steel substrate under different plasma spraying conditions. For comparison, Mo splats were also deposited on Mo surface. The substrate surface was polished prior to deposition. The powders used have narrow particle size distribution. The results show that the morphology of splats depends not only on particle temperature and velocity, but also on the thermal interaction between molten particle and substrate. The diameter of almost all splats formed by completely molten droplet on flat surface in the ambient atmosphere was less than 2 times of droplet diameter. The splat observed was in fact only a central disk-like part of an ideal disk-like complete splat with the outer annulus ringed. The typical pattern of such splats was the split type presenting a small hill structure on stainless substrate surface. With large Mo particle, the preheating of the substrate has no effect on splat morphology. On the other hand, disk-like type Mo splat with a reduced diameter of a dimple-like structure at the central area of splat was formed on Mo substrate. Based on the experimental results, a surface-melting-induced splashing model was proposed to explain splat formation mechanism.