This research casts the light on the Saljuq minister Nizam al-Mulk and his role in the political, administrative and cultural life. Despite poverty, he fulfilled his ambition of being a minister by his intelligence and personal qualifications. During his ministry, which lasted thirty years, he achieved a lot in security and justice. He abolished taxes and established the feudal military system instead of the salary system. He crowned his achievements with his book "Seyasat-nameh" (Kings' Policies) which includes the sum of his experience in administration and policy. In addition to that he encouraged education by establishing libraries and schools, paying salaries for teachers and students, honoring the Sunni scholars especially the Shafiate followers, as he was one of them. That led the Ismaelia (A Shia group) to rebel against him accusing him of being fanatic, and the Sultan accused him of political tyranny which led to his assassination.