Abstract: A horseshoe shackle is the one component of fan tower hoist, which fractured during the process of lifting tower. The macroscopic analysis, chemical composition analysis, mechanical property test, metallographic examination, hardness test, scanning electron microscopy analysis and finite element simulation were used to analyze the reasons of fracture. The results shows that the crescent-shaped external gap formed during the shackle manufacturing process, and poor heat treatment, resulting in lower toughness of the material. And then, the damaged gap became the stress concentration point in the lifting process, and the instantaneous fracture occur when the crack propagate to the critical value.