Abstract: By means of chemical composition analysis, fracture analysis, hardness test and metallographic analysis, the fracture causes of a car parking pawl were examined and analyzed. The results show that, the fracture of the pawl belongs to brittle fracture, the main reason is that the surface layer in the carburizing and quenching layer is oxidized, which leads to the crack at the arc transition of the pawl with weak stress under the action of working stress.The grain size of the material is very uneven and individual grain is unusually coarse, which leads to the formation of coarse martensite after carburizing and quenching.It increases the brittleness of the material and leads to brittle fracture.