Abstract: The future battlefield will be in space, "Space Military Forces" will also be a decisive military power in the 21st century. In 2007, an ASATs test of China has been criticized in the international arena, but through the analysis of the Article IV of the "Outer Space Treaty," as well as the U.S. military development in outer space. This article aims to demonstrate that developing ASATs did not breach outer space law from the perspective of international law and China has a legitimate need to have done so.