Abstract: In the process of hoisting 43.4 tons transition section of a container, the shackle of a lifting tool fractured. Through the chemical composition analysis, fracture morphology analysis, metallographic examination, hardness testing and so on, the fracture reasons of the shackle were analyzed. The results show that: the fracture of the shackle originated from the defects on the surface; in addition, the improper heat treatment process led to the inhomogeneous structure distribution, coarse grains, and ferrite precipitation along the boundary; these were the main reasons leading to the shackle fracture during the loading.