Environmental protection and economic development are obviously not only limited to the natural science area, but also deeply involved in the interplay between social science area and the geopolitical studies. Today, competition between countries mainly exists in the forms of competition for energy and other resources, the advancement of science and technology and the harmonious development between man and nature. The important marine strategy in contemporary society for a nation is how to acquire peaceful access to a harmonious marine environment to improve the overall national competition without breaking global peace. Harmonious marine environment, and its protection and economic development are discussed in the article. In combination of Mahan’s sea power theory with current developmental trends of new ocean century, the new three-stage theory is creatively put forward by the author to gain marine rights and interests, meaning three important elements of harmonious ocean view theory in modern international society, which are inter-coordinated, inter-connected and interacted.