Myth is thinking and reactions of the first man in the face of natural disasters and therefore the people were ambiguity to understand the causes of these accidents then their reactions to those events, along with the fear. The fear caused that they assume a God for everything to resort to it due to safe from accidents. The formation of myths in human societies have been based on the principle so in the myths of different nations, similarities can be seen. Among the Nations legends mythology, Iran and India are most similarities due to cultural commonalities. This research is analysis the common elements with considering the assumption of common themes between the Ramayana epic and Shahnameh in two characters of Siavash and Rama. Unity of these two mythical stories are outbreaks of mythological similarities in the two main heroes, the battle between good and evil, loyalty to the covenant and the covenant, fire-proof judged for show guilty and the innocent, the bravery and courage force, Cum control of the heroes fate, love, hate, the intrigues and conspiracies stepmother-in-exile of Rama and Siavash and entrusting their education to another in teenage period, Semi-divine eternal immortality of the soul heroes that to discuss it in a descriptive- analysis study of the story of Siavash in Shahnameh and epic Ramayana of Valmiki paid artifact. Methods of this study are based on the findings of the library and descriptive-analysis. Research results show that many common features of these two stories are same and the myth of Rama and Siavash common is a strong reason beliefs rooted influence of Aryan on the formation of these two stories.