Surface tension is the main driving force of film leveling, but the poor surface tension is the main source of film surface defects. It is very beneficial to improve the surface tension of the film and achieve the balance of the surface tension, but it can not be achieved. So people have to reduce the surface tension of the film to eliminate the surface tension difference, control the surface state of the film, and eliminate the surface defects. For example, eliminate the Bernal vortex to prevent the generation of flowers and orange peel. Eliminate the gradient difference of surface tension on the coating surface to prevent the formation of shrinkage cavity and corrugation. Reduce the interfacial tension between the coating and the substrate, enhance the distribution of the coating, improve the adhesion, reduce or eliminate the shrinkage caused by the substrate. Silicone oil and organic modified polysiloxane are widely used as surface state control agents in coating industry, which can basically eliminate surface defects caused by poor surface tension.