The invention discloses an additive of removing catalytic-cracking regenerated flue gas pollutant and a preparation method of the same and especially discloses a multifunctional additive of removing sulfur oxide and nitrogen oxide from the catalytic-cracking regenerated flue gas at the same time and a preparation method of the multifunctional additive. In the invention, magnesium aluminate spinel, a hydrotalcite-like compound and pseudo-boehmite are modified by rare earth elements, and then are added with a binding agent to form high-solid-content slurry liquid. The high-solid-content slurry liquid is subjected to spray moulding, drying and roasting to prepare an additive carrier being high in hydrothermal stability, and then the additive carrier is impregnated with noble metals in a manner of equivalent-volume impregnation. The impregnated carrier is finally subjected to secondary roasting to prepare the additive. The additive is good in hydrothermal stability, is good in activity durability, is long in service life, is free of components, such as vanadium, iron and the like, being harmful to a catalytic-cracking catalyst and is better in performance.