The utility model provides a simple structure, improvement work efficiency's that can be very big pipe welding machine, the technical scheme who adopts does: a pipe welding machine, motor and decelerator are provided on the support, the output shaft of motor and decelerator's input shaft, and decelerator's output shaft is connected with the input of first support frame, the action wheel of first support frame and driven pulley all activity are provided on the first support frame, and first support frame body upper end is provided with a plurality of regulation holes, and the first driven pulley of the structure of second support frame and second driven pulley all activity are provided on the second support frame body, and second support frame body is the same with the structure of first support frame body, and second support frame body and first support frame body set up relatively, can be corresponded the joint on cooperating the arc holding surface of formation by action wheel and driven pulley, first driven pulley and second driven pulley by the welded pipe, the utility model discloses but wide application in the pipe fitting field of welding.