Because Semi-Armor-Piercing warhead has tremendous destroying effects to thin armor targets, a method to study self-forging-fragment’s spatial movement and damage effectiveness is put forward for the needs of research. Based on researching and analyzing the producing mechanism and moving regularity of semi-armor-piercing warhead’s self-forging-fragments, the fundamental model is built up. The model can provide some reference to study self-forging-fragment’s spatial movement.