The ammunition of shrapnel often adopts unguided fuse, carry out simulation research on omni directional mechanism sensitivity. Establish dynamic model of omni directional firing mechanism based on ADAMS, research the relationship between inertial motion and time under different inertial material density, collision angle among different ammunition and different inertial force. Analyze the validity of touch ground response equipment of the mechanism model. The results show that material density of the inertial equipment and the collision angle have influence on the sensitivity of the mechanism, and the higher density material of the inertial equipment plays an active role in improving the sensitivity of the mechanism under the suitable condition.