The emergence of religious phenomena, namely "The Synods" in the history of Christianity, was entirely or mainly meant to oppose innovations and to create a relative unity in early Christian society; especially that the Christian early centuries experienced variety of nations and ethnicities and hence, variety of tendencies, religious sects and pseudo-religious sects. The study and analysis of the bases and causes of formation the first synod in Christian history-“The Council of Nicaea”- is counted as one of the greatest topics and courses in Christian history and theology. The Council of Nicaea, both, intended to resolve the basis debates and arguments in Christian beliefs and prepared the ground for further developments in this tradition. Protecting religious and political unity of Eastern Roman Empire in the fourth century, although taking stands about ideas of Arius (256-336) and announcing them as innovatory were only one of the purposes of The Council of Nicaea, yet it was one of the greatest of them, in a way that after publication of the Declaration of Athanasius and the clear stance of council against Arius, the Arianism movement left its impacts on Christian history as an important event. In this article, whilst we study the ideas of Arius- especially his ideas about the essence of Trinity’s second person- we also analyze the reaction of other influential movements in that time especially the official viewpoint of the Eastern Orthodox Church and through this we talk about the surrounding and further developments of this movement.