In the Age of Exploration, after the conquest of Malacca in 1511, Portugal had got information on China and steered its way to China. While Ming Dynasty put The Superintendency of Merchant Shipping(市舶司) in Canton which allowed foreign ships only for a tribute as `조공일원론`, local officials allowed its foreign trade in remote Tamao(屯門) or Nantou(南頭) which was 100km far away from Canton in reality. Staying in Tamao, Portugal sent Tome Pires to Beijing. But Beijing authority changed its attitude to Portugal, showing its wariness and boiling debates on banishment. This controversy led foreign policy to take a tough line through the death Zhengde Emperor(正德帝) and the appearance of Jiading Emperor(嘉靖帝) who oriented to Confucianism. In the meantime, the first and second Tamao battle occurred and Portugal was defeated in the war, being withdrawn to the ocean. On the other hand, the foreign policy of Ming Dynasty in early ages `tributary system monism(朝貢一元論)` which is `Tribute=Maritime Embargo Policy`. Following a brisk foreign trade, it is necessary to allow mutual trade(互市) gradually. mutual trade(互市) is a certain amount of tax collection for a trade through The Superintendency of Merchant Shipping (市舶司). It was classified by ① `tributary mutual trade(朝貢互市)` and ② `non-tributary mutual trade(非朝貢互市)`. In the middle of Ming Dynasty, ② was quite extensive and distinguished by The Superintendency of Merchant Shipping from Private Trade. At a time these debates on `non-tributary mutual trade(非朝貢互市)` were growing, Portugal timely came to China. However, expressing antipathy to the attitude and power of Portugal, Ming Authorities ceased its `non-tributary mutual trade` and returned to `tributary system monism(朝貢一元輪)` firmly. In this process, The Tamao battle broke out. Also, this naval battle was served as a momentum to make `tributary system monism` as a basic principle for foreign policy of Ming Dynasty firmly. Giving up the legal trade with China, Portugal caused many troubles such as a secret trade along the coast in China, joining with Japanese. In order to embrace them in a system, Ming Authorities had no choice but to choose the openning of Yue-Port(月港). From Ming`s perspectives, it was not a full permission to Private Trade but a series of trial to recover the marine order in a way of embracing Portugal as a `non-tributary mutual trade(非朝貢互市)`