Abstract: A non-magnetic steel logging cable drum broke during the logging process at a certain wellhead. The frature reasons for the drum were analyzed by macroscopic observation, chemical composition analysis, scanning electron microscopy analysis, metallographic examination, and mechanical property testing. The results show that the drum experienced fatigue fracture, which originated at the groove on the inner wall of the drum shaft. The mechanical properties and chemical composition of the drum were unqualified, the drum wall thickness was uneven, there were a large number of casting defects at the fracture, resulting in poor fatigue resistance of the drum. There was stress concentration at the drum shaft diameter, under the action of alternating stress, cracks initiated and expanded, ultimately led to fatigue fracture of the drum.