The utility model relates to a safety protection device of a chimney, which is suitable for the safety protection of a concrete chimney of a catalytic cracking (hereinafter referred to as catalysis) device in a refinery plant. The utility model discloses that the device has a supercharging air conveying system that is connected in series with the gas duct of a high-temperature smoke removing chimney, the supercharging air conveying system is provided with a supercharger, the main air at the inlet of the supercharger comes from the main air blower of a catalytic device, a flowmeter is installed on the outlet pipeline of the supercharger, a barometer is arranged on the rear pipeline of the flowmeter, a supercharging air pipeline behind the barometer is divided into two branches which meet in front of a chimney inlet with the gas duct of the high-temperature smoke removing chimney at the outlet of a catalytic smoke machine, or with the gas duct of the smoke removing chimney at the outlet of a boiler; a blind plate is installed at the rear part of a baffle door on the gas duct of the smoke removing chimney at the outlet of the boiler; two supercharging air injection points are symmetrically distributed on the two sides of a chimney inlet gas duct behind the blind plate. The device has a simple technical process, is easy to operate, runs reliably, and can effectively prevent smoke containing SO2 from entering the interior of the chimney, reaches the standard of environmental protection in operation, and guarantees the safety of the chimney.