As a nation in the peninsular Southeast Asia, since the AD-previous centuries. the cultures of Dong Son, Sa Huynh, Oc Eo-Phu Nam etc. were established in the Vietnamese territory. The owners of these cultures manifested obviously marine culture, and sea - directed thinking. Through trading ways on the sea, the ancient cultures created many connections to the cultural and civilized centres in the Orient and the World. Managing the. sea space rich in development potential, with the naturally famous harbors, and important trading position,. the Vietnamese Sea become early to the living environment and the decisive source for the economical and cultural exchanges to the outside. Ending Chinese domination and beginning independent era, the monarchical dynasties such as Ly (1009 - 1225), Tran (1266 - 1400), Le So (1428 - 1527), Le-Trinh in Dang Ngoai part and Nguyen Lord ( in Dang Trong part, XVI - XVIII centuries) etc. had the deep awareness on sea, sea-island sovereignty, and foreign economy for the country's development. Realized the development tendency of the world's economy by the government in Dang Trong part, the Nguyen Lords early chose and focused to strongly develop the economy of foreign trade. By this, Dang Trong part was becoming a prosperity kingdom, and a big centre of foreign trade in Southeast during a short time. Building the strongly economic basement included foreign trade contributed to the new economic aspect in Dang Trong part not only, and established the essential conditions for this government to consolidate its power, expand the country's territory, and defend stably the national sovereignty.