The invention belongs to the technical field of fire protection and particularly relates to a fire retarding method and a fire retarding device for an aerosol fire extinguisher. Due to the adoption of a fire retarding baffle, a fluid guide wall and a smoke through hole which is processed on a horn mouth, flames can be retarded, hot aerosol smoke can flow smoothly and is not sprayed explosively due to excessive pressure, and the smoke concentration and the strength of air pressure at a nozzle cannot be reduced, so that the fire extinguishing efficiency of a hot aerosol fire extinguishing device can be guaranteed. By the fire retarding method and the fire retarding device, flames can form vortex on a part close to the nozzle, and the kinetic energy of spraying is reduced to ensure that the flames are sealed in an internal cylinder of the aerosol fire extinguisher. The principle of the aerosol fire extinguisher is simple, and the original structure is not changed greatly. The fire retarding device is simple, and only a simple heat resistant shell is needed, so that the fire retarding device is low in cost, convenient to assemble and can be industrially produced conveniently.