The Proliferation Security Initiative (PSI) was first announced by U.S. President George W. Bush as a step against the proliferation regime by which authorizes the interception of planes and ships carrying suspect weapons of mass destruction (WMD) cargos. However, the proliferation of which WMD is a serious threat to international security and peace, American can not do it alone. U. S. needs the international cooperation with international community. The U.S. and its PSI allies have inventively used plenary meetings, expert discussions and joint operation exercises to increase PSI’s effectiveness. This paper explores the fundamental background, operational structure, related countries’ roles, legal basis, and prospects of the PSI.