Abstract: A series of tests and analyses were carried out on the failure sail plate by means of Brinell hardness tester,universal material testing machine, metallographic microscope and scanning electron microscope. The fracture surface was analyzed by SEM. The results show that the Brinell hardness, tensile strength, microstructure and spheroidization rate of the sail plate meet the technical requirements. The fracture surface is one-off brittle fracture and the whole fracture area is cleavage fracture. The huge impact overload is the main cause of the fracture. After improving the safety factor of the sail plate, it meets the use requirements and the early fracture problem is solved.