Abstract: Influenced by human activities, the order of destroyed degree of the desert ecosystem in Mongolia is steppe desert>typical desert>extremely arid desert. The destroying ways includegrazing, firewood gathering, covering of roads, urban and industrial construction, opencastmining, land reclaiming, negative effects of irrigation, etc. The destroyed degree of the pas-ture ecosystem is closely related to the distance from the centres of economic pursuits. In plant-ing industry, dry farmland can be easily eroded by wind, so the loss of humus is serious; someadvantages may be brought about but some negative effects may occur also in irrigated farm-land. Forest fires and deforestation are the main causes of the destruction of forest ecosystem, the degree, recovery speed and evolution orientation are different frorn various regions. Precipi-tation fluctuation results in an increase or decrease of humidity, a dry or humid period is rough-ly for 20 years in Mongolia. In this paper, sorne features of the natural conditions, the maintypes and trends of the ecosystems in Mongolia are discussed by extracting, translating, stuel-ing and editing the relating literature. Among the many types of Republic of Mongalia, thedesert ecosystem, pasture ecosystems in the people's ecosystem and agricultural ecosystem aremainly discussed in the paper.

Key words: desert ecosystem, pasture ecosystem, agricultural ecosysten, forest ecosystem, Mongolia