The present invention discloses a fast inflating air pump, including a housing, an inflating tube, an inlet tube, a motor, a transmission assembly and a controller housed in the housing. A blower is arranged in the inlet tube for increasing air pressure to the inflating port. A piston is at least partially contained in the inflating tube, and the piston is driven by the motor via the transmission assembly so as to slide back and forth linearly for increasing air pressure in the inflating tube. A one-way valve is installed in the communicating pipe for only allowing air flow into the inflating tube. The controller instructs the motor to drive the piston to slide back and forth in the inflation tube on condition that the blower stops working until the air inflation pressure increases to a predetermined threshold, then the controller instructs the motor to stop operating.