The army’ s security-based measures in Reza Shah’ s period in the current history of Iran, is subjected to two diverse judgements. According to the first attitude, he could retrieve the security in Iran. The proponents of this attitude mostly base their judgement on the police force which could confront some of the tribal and local rebellion and the widespread banditry. having approved of this attitude, the other aspect of it will be left neglected; since Reza Shah’ s army was itself one of the key factors in the country’ s chaos, and most of the political suppression was applied using the very military power of the new army. Basically, Reza Shah’ s regime had an antisocial approach. In fact all the military elements and the modern army which were responsible for the internal-security establishment were privately serving to his own interests. This article based on documents and librarywise attempts to scrutinize the function of the most important security agent of Reza Shah’ s army by expressing the security establishment in the first Pahlavi era. The findings of this study demonstrates, In Reza Shah’ s period, the army failed to fulfill it’ s prime function and in reality, it functioned as a police force and in doing so, after combating the insecurities caused by bandits and the tribal conflicts, cruelties and the widespread corruption of the officers and leaders, still caused more profound and widespread insecurity among a diverse number of people in society.