Abstract Spray forming can be used for rapid fabricating parts and moulds of ceramic, metal and alloy. The coating property has a dramatic effect on the quality and service performance of the products. Researches on improving the coating quality are mostly focused on spraying technology internationally. However, it is necessary to study further on the mechanism of coating forming and influencing factors of coating quality based on the process of particle atomizing, splashing and flattening. In this study, the sprayed particles have been collected to analyze the atomization state of the particles in arc spray forming, and the processes of the particles impacting on the spray mould, splashing, flattening and solidifying have been investigated. And the microstructure of spray-formed parts and the factors influencing the working surface roughness have been analyzed. The experimental results show that the preheating temperature of the substrate influences the particles flattening configuration significantly. When the preheating temperature exceeds the critical value, the infiltrating of the particles turns high and the splats of the coating appear sandwich, otherwise the shapes like outstretched fingers. The coating with a compact structure can be obtained by choosing reasonable atomizing pressure. At the same time, the corresponding coating porosity is low and its micro-hardness is high. This research has an instructive effect on the optimizing control of the coating quality.