In the Ming and Qing Dynasties，the Tanka living along rivers and oceans are still took fishing as their occupation. Because of the favorable conditions and advantages，they took part in the early sino-foreign trade and opium smuggling activities，and even became the main force of maritime transportation and trade. Although they had a strong motivation for making a living and seeking profit at the beginning，they unconsciously acted as the middleman between China and the world during the long-term maritime trade.