1. "Yongjia mourning" period occurred in Yongjia period of Western Jin Dynasty. Corrupt rulers brutally exploited and oppressed people of all ethnic groups, thus making people in the Yellow River basin displaced and forced to migrate to the Jianghuai basin on a large scale (mainly into Jiangsu, Anhui, Hubei, Sichuan and other places). The population moving south is about 900,000, which has changed the pattern of large population in the north and small population in the south since Qin and Han Dynasties. The population in the south has increased rapidly, which has promoted the rapid economic development in the south. This is a landmark event that the population distribution center of China has shifted to the Yangtze River basin. 2. The "An Shi Rebellion" occurred in the Tang Dynasty, and about 6,543,800 people moved southward, which fundamentally changed the pattern that China's population distribution was concentrated in the Yellow River basin, and the proportion of population distribution between the north and the south of China reached a balance for the first time. 3. The "Jingkang Rebellion" happened in the Northern Song Dynasty. 1 125, Jin destroyed Liao and began to attack the northern song dynasty in the south. The Yellow River basin has become the main battlefield. Every major war caused a large number of residents in the Yellow River basin to migrate to the Yangtze River basin, mainly to Zhejiang, Jiangsu, Hubei and Sichuan, which was the largest stage of population migration in the late Northern Song Dynasty. 4. During the "Jin Yan" period, Jin tore up the contract with the Song Dynasty and invaded the south on a large scale, forcing the residents of Huaihe River basin to move south to the Yangtze River basin, mainly to Zhejiang, Jiangsu, Hunan, Jiangxi and other places. 5. During the period of "Mongolian soldiers invading south", Kublai Khan and others arrived at the position of the khanate. 1273, a large number of Mongolian soldiers invaded south and launched a war to destroy the Southern Song Dynasty. The main battlefield is in the middle and lower reaches of the Yangtze River, and a large number of local residents have moved to the Pearl River basin to escape the war, mainly in Guangdong, Guangxi and Fujian. 6./kloc-After imperialism invaded old China in the late 9th century, China, Russia and Japan competed to expand their power in the northeast, build railways and plunder resources, which required a lot of labor, forcing North China to go bankrupt. Farmers moved to the northeast one after another, especially in Shandong and Hebei provinces, with the largest number of farmers moving in between 1923 and 1930. In addition, there are many farmers in Gansu, Qinghai and Xinjiang in the northwest, such as Henan and Shaanxi provinces. 7. After the invasion of Southeast Asia by European and American capitalism in the period of "Southeast Coast Going South to Southeast Asia", in order to plunder the resources of Southeast Asia, bankrupt farmers were recruited from China as the labor resources for developing colonies, and the labor force from China was sold, which led to a sharp increase in the population of Southeast Asia. The plain in the middle and lower reaches of the Yellow River is the birthplace of the Chinese nation. Since the Qin and Han Dynasties, the population of China has spread from the middle and lower reaches of the Yellow River to the surrounding areas, with emphasis on the Yangtze River basin and the Pearl River basin in the south. The population migration caused by "An Shi Rebellion" fundamentally changed the geographical distribution pattern of China's population, making the population in the south surpass the population in the north for the first time, and the population distribution center in China shifted from the Yellow River basin to the Yangtze River basin for the first time. The most direct causes of population migration in the history of China are migration, war and natural disasters. For example, in the history of our country, every time there is a war or famine, it will cause a large-scale population migration.