The present invention relates to a method and an auxiliary device for precision positioning of welded type nozzles. The auxiliary device for precision positioning of welded type nozzles includes a plurality of alignment tips and an alignment bar. Each alignment tip is connected to a welding adapter and extends a distance. The alignment bar is combined with the alignment tips so that first positioning portions of the alignment tips are aligned with a plurality of second positioning portions of the alignment bar, and after the alignment bar is combined with the alignment tips, a correction distance between an end surface of the alignment bar and a center line of a main pipe header in a longitudinal direction is larger than a length of an assembled nozzle after a nozzle tip is combined with the corresponding welding adapter. In this way, the geometric positions of the nozzles can be accurately corrected.