Abstract: The material properties of bullet head have an important influence on PTFE/Al bullets penetrating into soil. To investigate the relationship between bullet head material and penetration depth, bullet heads made of nylon, aluminum, 45#steel and PTFE/Al were shot by ballistic gun and penetrated vertically into soil. By contrastively analyzing the penetration energy per unit distance, the mathematical relation between the location of the biggest cavity and penetration depth was obtained. The result shows that aluminum bullet head need minimum energy, and delay PTFE/Al active time will enhance penetrating depth.