The author suggests the following two key priciples ought to be followed in our human economic activities: 1) to keep the equilibrium relationships among the four variables──natural resources, the environment, population, and development, and to establish a global carrying-capacity of renewable resources for humanbeings. 2) to develop the superiority, i.e. to develop the favourable conditions of each specific area in its natural, economic and technical aspects as a whole. To meet the requirements for the development of national economy, it is preferable to develop in areas most favourable in conditions the most suitable agricultural sectors and crops so as to put the minimum cost and to achieve maximum economic benefits.In accordance with the principles mentioned above, the paper discusses the changes occurred in Hainan Dao in its of agricultural development over the past 30 years, particularly the changes of equilibrium among the four variables------natural resources, environment, population, and development, and that of global carrying-capacity of renewable resources for humanbeings, the unfavourable natural conditions, fragility and superiority of the area. Based on its superiority, the author proposes the orientation for developing comprehensive agriculture of island, and for its vealization correspondent policy and a aeries of measures needed to be adopted.