Abstract: The linkages connecting wing flap and main wings have fractured for several times in recent years. But the clearances conform to the standard during ground inspection, and no heavy landing or overspeed warning were not found in flight record. Fracture observation, mechanical analysis and finite element simulation were used to investigate the failure cause. The result shows the fracture surface presented dimples and shearing fracture characteristics, which are the characteristics of overload fracture. Mechanical analysis shows that elastic instability occurred to the linkages under a low compress stress. Finite element simulation shows that during elastic deformation, significant lateral displacement in middle part of the linkage was found. It is assumed that the lower strength of the connecting rod is the main caused for the failure. According to the results above, new connecting rods with higher strength have been adopted and since then such failure hasn’t taken place again.