The utility model discloses an expanding assembly ware in semi -automatization for pipe fitting butt joint, including automobile body (3) that set up the bottom road wheel, the front end of automobile body (3) sets up two pole pneumatic cylinder (1), the both sides piston rod of two pole pneumatic cylinder (1) props up interior expand (pattern) match (2) of the one semicircle type that has pushed up respectively, ground engaging wheel's motor (four to six -tenehs) has also been set up on automobile body (3), the rear portion of automobile body (3) is upwards supported there are zhi dingfang topple wheel body (4). The utility model discloses a machinery semi -automatization production model replaces traditional artifical production model, and to carry out the make -up unit right, and mode line up that the pipe of two butt joint expands in by the hydro -mechanical when the assembly carries out whole circle simultaneously, with unfitness of butt joint control in standard range, and then satisfy the requirement of pipe assembly quality, guarantee the root of weld quality that takes shape, improve assembly efficiency. The utility model discloses can effectively solve the wrong limit phenomenon that the pipe produced when the assembly, guarantee the shaping quality of root of weld, improve the production efficiency and the assembly accuracy simultaneously.