The present study titled "the effects of social and economic modernization on the occurrence of the Constitutional Revoloution in Iran" seeks to present the economical and social innovation achieved during Qajar period and also discusses the role and effects of these innovations in encouraging Iranian people for political participation and overthrowing Qajar dynasty. this study shows that the innovations occurred during Qajar period caused changes on old customs and introduced modernism and new styles of social life. It also, taught new concepts like freedom and law to the Iranian people. Struggling to achieve the above goals and to protect the country, the people decided to become united. By establishing the parliament, they limited the power of the monarchy and made a way for people to participate in governing their country. Today this unity and interference is called political participation. The method of this research is historical comparative and the method of data gathering is library and documentary.