Abstract: The impact test was completed under high speed impact load, and the sample and impact blade would produce a high internal stress. Generally, the sample would have a pre-notch, and part of the impact energy would be absorbed by the sample along the notch direction, and part of the impact energy would be absorbed by the impact blade. When the energy absorbed by the impact blade exceeded the elastic deformation, the blade would have plastic deformation or even fracture. By studying the selection of impact sample, impact blade, impact testing machine and the test process, the fracture causes of impact blade were found out, and appropriate control methods were proposed.