Another view is that the fundamental reason why China's foreign trade center moved south in the late Tang Dynasty was the development of productive forces. The focus of China's early foreign trade was located in the Yellow River basin and Hexi region, which was consistent with the backward productivity level in this period. On the one hand, restricted by the low level of productivity development, the scope of regional economic development is small. Before the Tang Dynasty, the economic development in the southern region was low, except Jiangdong, most areas were undeveloped virgin land. At the same time, the Yellow River basin has been developed to a higher degree, thus becoming the focus of the national economy. There are not only relatively developed agriculture, but also handicrafts, especially silk weaving, which had a considerable production scale in the Han Dynasty. The products produced are rich in variety and excellent in texture, which provides an important material basis for the development of foreign trade. On the other hand, the ability of early human beings to conquer the ocean was low, and the risk of maritime transportation was huge, so the Northwest Silk Road became the best channel for China's foreign trade. At the same time, the commodities of early Sino-foreign trade were mainly luxury goods. For example, China exports mainly silk, while imports are mostly exotic foreign goods such as jewelry and ivory. This kind of goods are usually small in size, light in weight and easy to carry, and can adapt to the transportation conditions in the northwest desert where camels are the main means of transportation. The Yellow River valley and Hexi region along the Silk Road have unique geographical advantages and have been leading the foreign trade history of China for thousands of years.