Recently, the ROC Coast Guard Administration (CGA) decided to purchase several Tuo-River class corvettes, so the term "Second Navy" has become popular in the political discussion. The reason why CG is called the "Second Navy" is its mechanism of convertible missions between peace and war. Hence, the article finds that CG's wartime missions are changed from supporting to fighting. In addition, the article finds that the U.S. and Japan's Coast Guard's war mission would only support navies, but do not join naval fighting even if they were commanded by national defense system in wartime. Moreover, CGA is difficult to accomplish wartime preparation owing to multiple reasons. To sum up, if the government equips CGA warships and orders them to combat in wartime, CGA would fail main missions and waste of national resources.