Iran is located in the heartland of the Middle East and surrounded by three concentric circles：neighboring countries，the Islamic world and the relevant major powers. As a small Islamic state with the ambition to become a major power，Iran has been pursuing continuously goals beyond her strength，thereby maneuvering among the above mentioned three circles. Though this Tri-circles Diplomacy has a grand tradition，it is beyond the reach of power and needs of interests to contemporary Iran，thus keeping the three circles in a state of crisis for Iran. However，in spite of the lack of reliable backing，Iran could always fight with major powers in crises with both open and secret means while not allowing the situations go wild；this in fact demonstrats the outstanding diplomatic strategy of Iran.