From the invention of writing at the end of the fourth millennium B. C. to the conquest of Alexandria in 330 B. C., Sumerian, Akkadian and Aramaic were used as lingua franca one after another in western Asia. Sumerian acted as lingua franca of Mesopotamia and southwestern Iran, Akkadian was the common language of western Asia and northern Egypt, and Aramaic was used in western Asia, Egypt and part of inner Asia. Military conquests were the main dynamic that Sumerian, Akkadian dialects and Aramaic became lingua francas, the advantages of the related cultures made them stand out among languages, and international communication promoted their replacement. Lingua franca was used as diplomatic language when western Asia was divided by powers, and it contributed to the communication of united regimes, and acted as an important tool to gurantee state apparatus work regularly.