Abstract: The phenomena of premature rupture of connecting bolt of restriction lock in fatigue test of a main hub central component are investigated through the analysis of macro-morphology, micro-structure, fracture characteristics and hardness testing. It is concluded that the fracture property of the failure part is unidirectional bending fatigue rupture which are caused by the reduction of bolt tightening moment and the processing quality of the transition area of chamfering angle of the bolt head. According to the analysis of the fault results, propose improvements are as follow: increasing the tightening moment of the locking bolt, increasing strength by the screw thread and the R area of the bolt head inverted arc rolling. The connecting bolt of the restriction lock of the central part of the main propeller hub is improved by the above measures, and no early fracture occurred during the entire fatigue test.