In 265, Sima Yan forced Emperor Weidi to give up the throne, and proclaimed himself the emperor. Sima Yan was the Emperor Wudi of Jin Dynasty. The state was called "Jin", which is known as Western Jin Dynasty in history with its capital at Louyang. Western Jin Dynasty troops wiped out Wu and reunified the country. In the early years of Western Jin Dynasty, the government implemented a series of policies to encourage farmers enthusiasm in farming, raising silkworm, reclamation of wasteland. Over a period of more than two years, the number of households and the total population increased by more than 1,300,000 over two years, and a brief prosperity occurred.

In order to keep the world of Sima family, Emperor Wudi of Jin Dynasty reinstated the ancient system of enfoeffment, and 27 kings from the Sima family were stationed around. Shortly, internal strife arose among the Sima family. The Eight kings including Lun - King of Zhao, Wei - King of Chu, and others were fighting for imperial power from 291 to 306, which lasted as long as 16 years. In order to strengthen their own power, the eight kings made use of the northern minority forces. Thus, Huns, Xianbei, Jies and other military forces pushed deep into Central Plains, and the northern regions experienced unprecedented upheaval.

In 304, Liu Yuan, leader of Huns, started a war and gradually took control of most of the land of Bingzhou. In 308, Liu Yuan proclaimed himself emperor in Pingyang (today's Linfen, Shanxi province), and sent Hun army overran Chang'an, captured emperor Mindi of Jin Dynasty, In less than 40 years, Western Jin Dynasty perished after a brief reunification.