This study was carried out to offer the basic methodology of the system and model toobjectively assess the natural ecosystem for environmentally friendly land conservation andpresent the alternative plan on establishing the environmental policy. The results of this studywere as follows.We selected four assessment factors associated with biotic, abiotic, qualitative, and functionalfactors. Also, there were extracted fifty-six indicators including density, total nitrogen, hemerobydegree, and goods production. The assessment factor showed that biotic one was veryimportant. The importance of indicators were analyzed that rare and endangered plant wasimportant in biotic factor, in case of abiotic, qualitative, and functional factors, organic matter,landscape diversity, and conservation of ecosystem were greatly important. The results of factoranalysis on the characteristics of indicators, classified biotic factor into six factors including astructural one, abiotic factor as a soil and physical one, qualitative factor as five ones includinghierarchical one, and functional factor as public and conservational one. In the results of analysis on assessment model, R-square of biotic factor was 51.7%, those of abiotic, qualitative, and functional one were each 58.4%, 44.2%, and 39.3%, and statistical problem was no existence. In
future, to develop the assessement model and methodology of sustainable natural ecosystem, we will have to achieve the integrated model and grouping by assessment factor.