The utility model discloses a flange nozzle stub is prefabricated machining tool fast, it includes: landing leg, backup pad, fixed stop, twist grip, drive shaft, slide rail, movable baffle and dipperstick, the lower part in the backup pad is fixed to the landing leg, fixed stop fixed connection is at the first end of backup pad, and is mutually perpendicular with the backup pad, the one end of drive shaft is passed fixed stop's shaft hole and is connected the twist grip, slide rail fixed connection is parallel to each other in the upper surface of backup pad, the extending direction and the drive shaft of slide rail, the last threaded holes and constant head tank that sets up of movable baffle, the screw thread of screw hole and the screw thread looks adaptation of drive shaft, the dipperstick vertical fixation is on fixed stop, and the extending direction of dipperstick is parallel with the drive shaft. Utilize the utility model discloses flange nozzle stub is prefabricated machiningtool fast can solve size consistency between the unified specification product to and guarantee the perpendicular of flange and pipeline axis, improved the construction quality and the aesthetic measure of flange nozzle stub.