With the arrival of Iran into the new historical conditions in the age of Qajar reign which was resulting from the Iranians’ confrontation with the modern civilization, the understanding of holders of thoughts on the situation of weakness and power of political sovereignty was gradually changed and they put forth different models to exit the Qajar absolute monarchy from the position of weakness and inefficiency.
However, finally, it was the idea of ‘Constitutional Monarchy” which was converted into the final political project of Iranian political modern thinkers to covert the absolute monarchy into the modern state. This research is an attempt to find out the causes of this event. Using the historical research methodology and applying the causative and rational elaboration, efforts have been made to respond to this question. The results of this research show that the defeat of the plan to establish a regulated absolute monarchy ,- due to different views and practices of the governmental administrators at Naseri and Mozafari ages and effective oppositions of the traditional elements of the state and society against the upper reforms which are in agreement with modern civilization models- , and the trend of daily weakness of Qajar absolute reign at Mozafari age , all made the modern thinkers- who used to emphasize on the necessity of law to administrate the government at modern age- to move towards the model of modern state resulting from the will of the nation and put forth the model of Constitutional Monarchy at public level as a final strategy to establish the modern state.
Key Words: Qajar Dynasty, Absolute Monarchy, Law, Modern State , Regulated Absolute Monarchy, Constitutional Monarchy.