Abstract: National Environmental Quality Decision Support System(NEQDSS) is an environmental decision support system based on the environmental protection of 52 cities which can imitate and predict environmental quality, and also compare projects. NEQDSS can provide scientific decision means and information for environmental management department to make up environmental quality control plans and related policies of either mid or long- term, This essay states generally the specification of function demand, the analysis of data demand and the system design. Simultaneously, it sums up the development technigues and expects the further development.