Due to the flow of the two great rivers Tigris and Euphrates, the land of Mesopotamia has long been the place of establishment and formation of great and magnificent civilizations. The Sassanid kings, who were the inheritors of these civilizations, made Iraq the center of their government and called it "the heart of Iranshahr". They were fully aware of the vital role of these two rivers in the economic prosperity of this land, so by implementing large and extensive irrigation projects, they quickly traveled the prosperity road and brought the interrivers to their development and prosperity terminus. With the fall of the Sassanids and the domination of the Muslim Arabs, the civil and irrigation system of Iraq did not change at the discretion of the second caliph, and this legacy was transferred to the Islamic era and caused the growth and prosperity of civilization in the early Islamic centuries. This article, with a descriptive-analytical approach, tries to investigate the issue of what effect did Sassanid irrigation and water supply projects have on the construction and development of the Mesopotamia? The findings of the research indicate that the Sassanid water supply projects continued in the Islamic era and the caliphs tried to expand this network by creating new artificial streams, and this issue not only caused rich tax profits in the Swad region, but also the establishment of large cities such as It provided Basra, Kufa, Baghdad, Samarra.