The utility model provides a longitudinal welded pipe preflex shaping testing machine. There be not the not enough of special preflex shaping testing machine in order to overcome current longitudinal welded pipe new product, the utility model discloses an on the frame is installed respectively to press, preceding feeder, back feeder, preflex mould, bender, exit tube machine, preceding feeder, back feeder, the axis of preceding feeder, back feeder and mobile Workbench's dead in line, install preflex mould or bender according to preflex, the process of bending needs on the press host computer, adopt the retooling frock to change the installation to preflex mould or bender, the last die crushion iron fixed mounting of preflex mould is on the slider of press, and preflex die holder fixed mounting is on mobile Workbench, the last mould die shank fixed mounting of bender bends die holder fixed mounting on mobile Workbench on the slider. The beneficial effects are that reasonable in design on a testing machine, improves longitudinal welded pipe forming technology experimental efficiency and quality with the flange preflex in the longitudinal welded pipe production process and the twice process integration of bending.