The present invention relates to a method of preparing thermal insulation expandable polystyrene particles and thermal insulation expandable polystyrene particles, and more particularly to a method of preparing thermal insulation expandable polystyrene particles which include preparing a mixture of expandable polystyrene particles and a thermal insulation material by mixing the expandable polystyrene particles and the thermal insulation material; preparing a mixture solution by dissolving chlorinated paraffin and at least one of a paraffin oil and a rubber resin in an organic solvent dissolving styrene; and softening a surface layer of the expandable polystyrene particles by spraying the mixture with the mixture solution, while stirring the mixture, and infiltrating the thermal insulation material, the chlorinated paraffin and the at least one of the paraffin oil and the rubber resin into the surface layer of the expandable polystyrene particles, and thermal insulation expandable polystyrene particles prepared by the same.