A method for regenerating a catalyst, comprising: spraying steam to a spent catalyst; and spraying dry ice particles to the spent catalyst, further comprising removing a poison included in the spent catalyst, after the spraying of dry ice particles to the spent catalyst, and wherein the removing of the poison included in the spent catalyst comprises penetrating dry ice particles into the poison, and sublimating the dry ice particles, wherein the term "steam" means a gaseous state of a liquid or solid material at room temperature, wherein the surface temperature of the spent catalyst is 25 °C to 50 °C, wherein the temperature of the steam is 100 °C to 500 °C, wherein the amount of the sprayed steam is 300 cc/min to 1200 cc/min, wherein in the spraying of steam to the spent catalyst, a liquid material is dispersed on the surface of the spent catalyst, wherein in the spraying of dry ice particles to the spent catalyst, the liquid material dispersed on the surface of the spent catalyst is frozen, and the dry ice particles are ground when colliding with the spent catalyst at a high speed, wherein the dry ice particles are sprayed at a speed of 100 m/s to 500 m/s, wherein, when the liquid material dispersed on the surface of the spent catalyst is frozen, cracks are formed in the poison included in the spent catalyst, wherein a decrease rate of the weight ratio of a poison to active components in the catalyst before and after the regeneration, according to the following Equation 1, is 30 % to 90 %: Decrease rate of the weight ratio of poison to active components before and after regeneration % = the weight ratio of poison to active components in the catalyst before regeneration − the weight ratio of poison to active components in the catalyst after regeneration / the weight ratio of poison to active components in the catalyst before regeneration ∗ 100, wherein the weight ratio of poison to active component is a value obtained by dividing the content of poison in the catalyst by the content of active component, and if the number of the poisons is 2 or more, the content of the poison means the sum of the contents of all the poisons, while if the number of the active components is 2 or more, the content of the active component means the sum of the contents of all the active components, wherein the spent catalyst comprises a selective catalytic reduction catalyst. spraying steam to a spent catalyst; and spraying dry ice particles to the spent catalyst, further comprising removing a poison included in the spent catalyst, after the spraying of dry ice particles to the spent catalyst, and wherein the removing of the poison included in the spent catalyst comprises penetrating dry ice particles into the poison, and sublimating the dry ice particles, wherein the term "steam" means a gaseous state of a liquid or solid material at room temperature, wherein the surface temperature of the spent catalyst is 25 °C to 50 °C, wherein the temperature of the steam is 100 °C to 500 °C, wherein the amount of the sprayed steam is 300 cc/min to 1200 cc/min, wherein in the spraying of steam to the spent catalyst, a liquid material is dispersed on the surface of the spent catalyst, wherein in the spraying of dry ice particles to the spent catalyst, the liquid material dispersed on the surface of the spent catalyst is frozen, and the dry ice particles are ground when colliding with the spent catalyst at a high speed, wherein the dry ice particles are sprayed at a speed of 100 m/s to 500 m/s, wherein, when the liquid material dispersed on the surface of the spent catalyst is frozen, cracks are formed in the poison included in the spent catalyst, wherein a decrease rate of the weight ratio of a poison to active components in the catalyst before and after the regeneration, according to the following Equation 1, is 30 % to 90 %: Decrease rate of the weight ratio of poison to active components before and after regeneration % = the weight ratio of poison to active components in the catalyst before regeneration − the weight ratio of poison to active components in the catalyst after regeneration / the weight ratio of poison to active components in the catalyst before regeneration ∗ 100, wherein the weight ratio of poison to active component is a value obtained by dividing the content of poison in the catalyst by the content of active component, and if the number of the poisons is 2 or more, the content of the poison means the sum of the contents of all the poisons, while if the number of the active components is 2 or more, the content of the active component means the sum of the contents of all the active components, wherein the spent catalyst comprises a selective catalytic reduction catalyst.