In contemporary Iran, sociological study of political phenomena does not have a long history. (History) Such studies in Iran after the Islamic Revolution are also new! (Background) Thus, all aspects of the sociological effects of social groups like religious groups in national, provincial, and urban scales on the components of political participation of the Islamic Republic has not been investigated and still, the overall picture is that governmental agencies, not social groups, can do whatever they like! (Problem) Lack of explanation of the aforementioned effects raises the following question: What are the kinds, amounts and shares of the social effects of religious groups on political participation of the Islamic Republic? (Question) Religious groups, as nongovernmental social institutions, enjoy deep status and acceptance in the minds and hearts of the people and consequently have effective functions like delegitimization. (Hypothesis) The authors of the present article have tried to show the effects of religious groups on components like elections, and political demonstrations and speeches as the significant instances of political participation of the people by investigating the role of elements like age, gender, ethnicity and referent groups in religious groups (Methodology) and present a new categorization of the overt and covert functions of religious groups by generalizing the results of the investigation of Shahriar religious groups. (Objective) These investigations show that: sociological elements of religious groups have increasing role on the increase and decrease of political legitimacy of the Islamic Republic system. (Finding)