First of all, the Tang Dynasty owned the world, and the Guanlong military group of the Li family mainly relied on the mighty force of the Kanto (now Shanxi, Hebei, Shandong and Henan), such as the Wagang Army, and the political beliefs of the Kanto scholars were all in Luoyang, because since the Eastern Han Dynasty, the Wei and Jin Dynasties have taken Luoyang as their capital, and they have been moved to Luoyang by Emperor Xiaowen of Wei after five chaos, realizing the unification of the north, and the popular will lies in the "world". From the south, Du Nan scholars are mostly descendants of Sima's powerful family in the Western Jin Dynasty, and their political beliefs are also in Luoyang. Secondly, economically, Xi 'an's farming conditions are not as good as Luoyang, which is the center of the Grand Canal, and its commercial prosperity is not as good as Xi 'an's. Because of the poor grain transportation and poor harvest in Guanzhong, the emperor of Tang Dynasty often moved the whole government agency to Luoyang, which was called "Eating the East Capital" and "Eating the Emperor". Third, Luoyang's position in culture is extremely lofty. From the linguistic point of view, the rhyme of Tang poetry is based on cutting rhyme, which is based on Luoyang pronunciation, not Kansai dialect. In order to win over the Kanto scholars, the Tang Dynasty set up an examination room in Luoyang, the eastern capital, and held a nationwide imperial examination. Generally speaking, Luoyang's position in the Tang Dynasty was worse than that in Shanghai today. The specific process was that Li Shimin, Emperor Taizong, ordered the restoration of Luoyang City, which was called Luoyang Palace. He came to Luoyang three times to handle government affairs and foreign affairs, and lived in Luoyang Palace for two years. On September 9th, the first year of God's will (AD 690), Wu Zetian established herself as the emperor, respected the holy god emperor, changed the country name to Zhou, made Luoyang its capital, and changed the eastern capital to the god capital, which lasted 15 years. Xuanzong of the Tang Dynasty reigned for 29 years, with Luoyang as its capital 10 year. In 904, Tang Zhaozong moved to Luoyang, and Emperor Aizong of Tang Dynasty was abolished by Zhu Wen in 907.