Abstract: The finished product of inner gear ring for a loader accidentally fell and brittle fracture occurred during transportation. The fracture reasons were analyzed by macroscopic observation, fracture analysis, chemical composition analysis, low power test and metallographic examination. The results show that the improper ring rolling process led to the deformation overburning of the inner gear ring, and a large number of circumferentially distributed fine holes and cracks appeared in the center of the inner ring. The machining exposed the defects in the core of the material, and a large number of vein structures were generated in the subsequent nitriding treatment, which greatly increased the brittleness of the inner gear ring, and eventually led to brittle fracture of the inner gear ring when it fell.