The Tang Dynasty was the first dynasty in China's history that began to communicate with foreign countries. However, due to the serious feudal ideology at that time, the country could not really open up. In addition, although Emperor Wendi of Sui Dynasty basically unified China under the leadership of Emperor Wendi of Sui Dynasty, the surrounding "small countries" were relatively evil, and the emperor of Tang Dynasty still needed to conquer those local forces. It was in Li Longji that the Tang Dynasty really reached the peak of China, when its economic strength was the most developed in the world. There is no need for too much trade and exchange with foreign countries. However, it initiated the zero era of China's contact with foreigners, which is of epoch-making significance.