The research aims to study the rise and fall reasons of the Qajar dynasty, with historical study and the descriptive-analytical method. Its emphasis is on the causes and factors of the decline and fall of this government based on Ibn Khaldoun's theory. Ibn Khaldun's theory has been chosen as a theoretical framework; By mentioning this point that in explaining the rise and fall of contemporary governments, including Qajar, it is necessary to revise this theory and consider new factors in this regard. For this purpose, in addition to evaluating and updating Ibn Khaldun's theoretical indicators such as nervousness, patronage, and types of corruption, attention has been paid to the new factors that are effective in the stability and especially in the fall of governments in the contemporary era, including foreign intervention and new technologies. The findings of the research compiled based on authentic historical documents show that the origin and continuation of Qajar with Ibn Khaldun's theory and its decline and fall with Neo-Khaldun's theory can be studied and explained more accurately, and they are more compatible with the existing facts and historical evidence.