This article is to show how the so-called solar monotheism appeared and developed in the Syrian local cults and creeds during the Hellenistic and Roman periods. It is well known thatseveral Oriental religions were diffused and established in the Roman Empire and that their idea of god was tending towards a sort of monotheism. I have examined how the oriental cults were able to reach such a unique stage of the religious evolution, by surveying their structure and the process of their formation especially in the intermediate destiricts of the propagation from the East to the West. Here I studied the Syrian native cults and showed their idea of god evoluted by itself up to the solar-monotheism and was amalgamated with that of other Oriental cults at last. The Syrian pagan monotheism thus established formed one of the strongest powers of the monotheistic trend in the Roman Religion.