Abstract: The gear hub of a gearbox cracked during the durability test. By means of macroscopic observation, chemical composition analysis, scanning electron microscope analysis, metallographic examination, hardness test and finite element analysis, the causes of the cracking of the gear hub were analyzed. The results show that the fatigue safety factor of the gear hub was lower than the standard requirement, resulting in cracking at the waist hole. After the waist-shaped hole structure was changed to a circular hole. In the subsequent test, the parts did not crack.