The invention relates to a preparation and using method of a composite coating used in a high-temperature high-chlorine and high-washing environment. The composite coating is composed of zirconite powder, titanium dioxide powder and monazite powder. The preparation method comprises the following steps that a base layer is subjected to coarsening treatment from bottom to top and in sequence; a bottom layer is sprayed with a supersonic flame; a self-healing intermediate coating is sprayed with an electric arc; a composite coating is sprayed with a supersonic flame; and hole sealing treatment iscarried out. The composite powder coating is prepared by mixing the zirconite powder, the titanium dioxide powder and the monazite powder. The obtained composite coating is good in corrosion resistance and erosion resistance in the environment with high temperature, high chlorine and solid washing, so that the composite coating is suitable for being used in the high-temperature high-chlorine high-washing environment.