Abstract: To investigate the fracture of the chain pin in the carbide tapping robot during a high-load impact test, macroscopic fractography, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), local finite element analysis, and cyclic loading bench tests were carried out. The results show that the crack initiated from the surface or subsurface region near the junction between the outer plate and the inner link. The fracture surface can be divided into a crack initiation zone, a crack propagation zone, and a final rapid fracture zone. The propagation zone is mainly characterized by quasi-cleavage facets, tear ridges, and locally friction-smoothed traces, indicating that the crack experienced a certain stage of stable growth before final instability. Non-metallic deposits enriched in C, O, and Ca were detected in fracture-related regions, suggesting that oxidation, wear, and particle involvement may have accompanied crack initiation and propagation. Local finite element analysis shows that a continuous high principal tensile stress band is formed on the surface of the key working region constrained by the chain plates under the present specimen configuration and loading boundary. The fracture location obtained from the cyclic loading bench test is basically consistent with that of the engineering failed sample. Overall, the pin failure is identified as a mixed fracture under the combined action of cyclic loading and impact disturbance, with fatigue damage participating in the fracture process. The results can provide a basis for structural optimization and surface anti-damage design of chain pins.