After the end of cold war, the roles and missions of nuclear weapons have been questioned due to the change of international politics. In the new century, should such possession and investment of nuclear weapons be worthwhile, if the old enemies vanished? What sort of nuclear forces would be of best interests for the nuclear weapon states in order to meet the challenges of new threats? These incentives constitute the necessity to re-examine current nuclear policy and revolution of nuclear weapon states. Among the five big states, the United States and Russia, which still possess the largest nuclear stockpile, seemly have been developing their new nuclear postures. The other three, although trying to do so, still show no clear patterns of change. As such, the author chooses the United Kingdom and People’s Republic of China as research subject. By introducing several topics of analysis, such as external influences, no-first-use principles, strategic and tactical roles, counterforce and countervalue, etc., it is the wish of this paper to demonstrate the continuity and change of the nuclear postures of both countries under the new international environment.