We have confirmed that in the thermal spraying of practical powder materials, the splat shape change transitionally to a disk shape from a splash shape on a critical substrate temperature, Tt. Substrate temperature increasing may accompany the change in a shape on substrate surface, because the changing effect is maintained till the substrate is cooled down to the room temperature. However, the essence of the substrate surface change due to the heating has not been clearly understood yet. In this study, AISI304 substrate was employed, and to make the chemistry on the substrate surface constant, Pt was coated after heat treatment. Pt coated substrate surface was analyzed precisely by atomic force microscope (AFM) and sessile drop method. We discussed about relationship between surface morphology in nano-meter scale and splat morphology.