Abstract: A system of controlling a flush toilet, which includes a first flushing channel and a second flushing channel, and the system contains: a depressurizing valve including an inlet connecting with an inlet pipe fitting, a first outlet, and a second outlet; a first water-supply pipe fitting employed to supply water from the first outlet toward the first flushing channel; a second water-supply pipe fitting applied to supply the water from the second outlet toward the second flushing channel; a first solenoid valve controlled to start and stop the first water-supply pipe fitting. The system also contains a second solenoid valve controlled to start and stop the second water-supply pipe fitting; a water pressure sensor for sensing a water pressure in the depressurizing valve and transmitting a pressure signal; and a control unit for receiving a flushing signal started by a user and the pressure signal from the water pressure sensor.