The invention discloses a chimney dust removing device. The chimney dust removing device comprises a chimney body, and further comprises a first rotating disc, a second rotating disc and a driving motor. The first rotating disc is located at the top end of the chimney body, and the second rotating disc is located above the first rotating disc and arranged parallel to the first rotating disc at intervals. The first rotating disc and the second rotating disc are connected by a connecting piece, and cavities are separately formed in the first rotating disc and the second rotating disc. Holes areseparately formed in the surfaces of the first rotating disc and the second rotating disc, and the driving motor is connected with the second rotating disc through a transmission mechanism. The chimney dust removing device can quickly remove dust particles in gas when a chimney emits the gas, avoids polluting the environment, and effectively protects the environment.