Abstract: Based on the environmental and natural characteristics of low-lying damp land in three-river plain, the plane ecological structure of "dryland field-paddy field-grass- field-fish pond" was formulated. While adjusting the ecological st ructurc, the ratio of input to output tor manpower auxiliary energy and the equilibrium of the farmland nutrients was analyzed or estimated scpcratcly, and the means of further development and perfection was put forward Analyses show that the system structure tends to be rational with its function increasing constantly, which indicates that the agrcccosystem of low-lying land changes in landscape. Moreover the integrated benefits increase every year. The study fully embodied the concept of rational ecological structure is the coordination of organism species and ecological conditions and it makes the use of resources reasonably, attaining the simultanous development of economic, ecological and social benefits.