The escalation of the Iranian nuclear issue coincides with a period of fragile international oil market. The spare capacity of world oil production declines，tension in the Middle East increase，the risk of oil supply disruption goes up，the international oil price tends to be higher and the world economic growth is threatened. Heavily depending on oil exportation，Iran is unlikely to hastily use the oil weapon. Oil factor serves rather as a constraining factor preventing United States and Iran from going to extreme.