During the reign of Emperor Wudi of the Han Dynasty, Confucianism and politics developed independently and merged into the pulse of the same era. As the "Confucianist school" in this period, Dong Zhongshu made great efforts to transform Confucianism and make it a practical ideology for the society and the state. His theory of "great unification" met the need of Emperor Wudi of the Han Dynasty to "run the world with virtue", thus completing the transition of Confucianism from top to bottom. However, due to the Han-Xiongnu War, Dong Zhongshu had no chance to put his ideas to good use in Xiongnu. Because of the foundation laid by Tang Meng road-cutting and Zhang Qian's investigation, Emperor Wudi of the Han Dynasty was determined to develop and manage the southwest Yi. Due to the special geographical position, the military strength of the southwest Yi was the weakest among the "Four Yi", and it would not pose a threat to the central plains dynasty. When the Han Dynasty concentrated its troops in the northern border counties, it was impossible to attack the southwest Yi as Xiongnu did. It provided space for the Han Dynasty to popularize Dong Zhongshu's idea of "great unification". The implementation of this Confucian thought is mainly embodied in the development of the road, the placement of officials and immigration. The first successful practice of Dong Zhongshu's thought in dealing with the problem of Yi-Xia was to manage the southwest Yi. The development of the Yi people in the southwest established the authentic status of Confucianism. Dong Zhongshu's thought of "great unification" became the dominant thought of the following dynasties, which has important reference for handling of ethnic relations, strengthening national unity, and developing national economy and culture.