The failure behavior and inducement mechanism of tungsten alloy fragments penetrating low carbon steel at high projectile velocities are investigated. The physical forms of 93W and 95W fragments after penetrating the low-carbon steel target at the velocities that higher than 1500m/s were obtained by using ballistic gun experiments. Using Scanning Electron Microscope (SEM) analyze damaged tungsten alloy fragments after the penetration, the result shows that, for low-carbon steel plate, when the penetration velocity of the tungsten alloy fragment is higher than 1500m/s, 93W tungsten particle is dimple-type transgranular fracture, 95W tungsten particle is quasi-cleavage transgranular fracture; Both 93W and 95W fragments were melted partially, the 50μm tungsten particles melted and condensed as less than 10μm spherical particles and arranged tightly. The macro phenomenon is the penetration of the whole damaged particles.