The invention discloses a piping extension system for tunneling. The piping extension system comprises a soil layer; the soil layer is provided with a launching shaft; one side of the lower end of the launching shaft is connected with a tunnel; the tunnel is internally provided with a tunneling machine; and one side of the tunneling machine is connected with a second telescopic mechanism. A slag outlet pump is connected to the tunneling machine; the slag outlet pump is connected with sludge feeding piping and sludge discharging piping; the lower ends of the sludge feeding piping and the sludge discharging piping are provided with a movable auxiliary tool; a sludge discharging pit is formed in one end inside the tunnel; a first telescopic mechanism is arranged on one side of the sludge discharging pit; and the sludge discharging pit is internally connected with a second fixed type sludge feeding pipe and a first fixed type sludge feeding pipe. In the piping extension system, with the tunneling process, the connector extension position of new piping does not need to be moved, piping materials do not need to be stored near the tunneling machine, and when piping connection is conducted, sweeping operation of sludge can be easily conducted.