0.008mm。 The J-integral moving theory with multiple loading and shaft straightening stroke increasing algorithm with single-edged crack were presented according to the elastic-plastic fracture mechanic theory and experiments analysis. During multi-step straightening, with the assumption of independent multiple loading, J-integral including two items of Je and Jp, and the crack blunting would promote the JIC increasing, the J-integral could be considered to move up slowly. Based on this view, the multi-step straightening stroke algorithm was built up to the shaft with single-edged crack. The straightening experiment resulted to the shaft with 3mm depth single-edged crack could prove the JIC moving phenomenon, and after 4 steps straightening to the experimented shaft, the initial 0.13mm bend value could be decreased to 0.01mm, while crack mouth opening displacement could be limited to 0.008 mm.