The invention discloses a speed-limiting device for an air inlet and outlet pipeline. The speed-limiting device is characterized in that a bearing (2) matched with the air inlet and outlet pipeline (1) is connected with a rotation shaft (3), fan impellers are arranged near the gas outlet end of the inlet and outlet pipeline (1) on the rotation shaft (3), a hole type sound-absorbing board (5) is arranged at the gas outlet end of the inlet and outlet pipeline (1), an air admission hole (6) is arranged at the gas inlet end of the inlet and outlet pipeline (1), a speed-limiting block (7) matched with the air admission hole is movably sleeved on the rotation shaft (3) through a spring (8), a speed-limiting device casing (9) is fixed in the position, corresponding to the speed-limiting block (7), on the rotation shaft (3), a plurality of balls (10) are arranged on the inner periphery of the speed-limiting device casing (9), and the speed-limiting block (7) contacts with the balls (10). The speed-limiting device of the invention has the advantages that the structure is simple and ingenious, the operation is convenient, the speed-limiting effect is good, and the air flow rate in the inlet and outlet pipeline can be automatically adjusted.