Iran with its historical heritage, religious values and cosmopolit structure is a archaic country of middle east. It saves it's importance throughout the history. In terms of these properties ıt's not only for ancient history but also with near future this country draw attention on itself. Such that this country witnessed significance incident at the beginnig of twenty century. The first incident is constitutional revolution happen between 1905-1911 years which in company with social events. In the meantime competitions of British and Russian on the Iran, adverse impact of the first world war and the most importantly in this chaos Rıza Khan come to power is another important incident. In this work initially accentualed is constitutional revolution. Although the aim of this movement was against autocracy and imperialism it serving for Russia and UK. The first world war is  another topic which is present. Although Iran wants be objective in this war they couldn't run away to be field of war big countries in their lands. In the meantime another topic is the country wasn't take importance except capital city in 1920 years Rıza Khan in Kazakh brigade quickly come to power in this chaos. He put an end to Qajar dynasty with a coup. In 1925 he established Pahlavi dynasty as a Shah of Iran.