A method and a system for vapor-based decolorization of a polyester textile are provided. The method includes: obtaining a textile to be decolorized by adding a phase change material to the polyester textile for mixing, and performing the vapor-based decolorization on the textile to be decolorized. An amount of the phase change material corresponds to a weight of polyester in the polyester textile, and a phase change temperature of the phase change material is not greater than a vapor temperature of a decolorizing agent used in the vapor-based decolorization.