When was the climax of the first great migration in ancient China?

Late western jin dynasty and early eastern jin dynasty.

At the end of the Western Jin Dynasty, the water conservancy in the Central Plains was in disrepair, and droughts, locusts and epidemics continued year after year. In order to seek food, people in the Central Plains began to migrate to the south. The destruction of the Eight Kings Rebellion and the impact of various ethnic groups in the west and north caused a greater migration tide. Yellow River Basin

At that time, the population of the Central Plains mainly flowed to the south, and some of them moved to the Liaohe River Basin or the Hexi Corridor far away from the Central Plains. At the end of Jin Dynasty, "Zhongzhou asylum seekers followed the sun and the moon", among which there were many cultural celebrities. Later, when the Central Plains was in melee, the Hexi Corridor was relatively peaceful. It became an important stronghold for the development of advanced culture of Han nationality at that time. The great population migration in the late Western Jin Dynasty was the result of social unrest, but it was objectively beneficial to the economic development and social progress of the resettlement areas and had a far-reaching impact on the economic, political and cultural development of later generations.

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Excerpted from China's history textbook.