Abstract: The present invention relates to a compulsory discharging device for exhaust of vehicle of the type in which a driving motor which has a propeller is mounted at the end portion of the exhaust pipe such that the exhaust within said exhaust pipe can be compulsorily discharged. The operation of the driving motor is controlled by a digital controller which uses a signal line to pick up the frequency of a high voltage line of an igniting coil. The rpm of said driving motor can be proportionally controlled with respect to the rpm of the engine. The output shaft of the driving motor is coaxially mounted with a propeller and a mixing propeller with which the exhaust can be mixed with fresh air to reduce the concentration of the exhaust. Then the diluted exhaust is discharged. The exhaust generated from the combustion within the cylinder can be effectively and completely withdrawn such that the performance of the engine can be increased. The residue of carbon is reduced and the power of the engine is increased.