The Faqih （Supreme Leader），as the core of the Iranian political institutions，has dominated the practice of the Iranian “constitutional government”. The Iranian regime’s tough stand in the nuclear issue is not only reflecting a tactics on the reins of power，also reflecting the challenge to the current international rules and pursuing the national interests. It is evident that the nuclear issue has directly or indirectly impacted on the Iranian political stability，social development and the national security，therefore，it underlies the limit of its tough stand. However，the nuclear issue hasn’t jeopardized the stability of the Iranian regime so far.