Heihe River system,originating from Qilian Mountains,is one of the important inland rivers in Northwest China.From Qilian Mountains in the south to Gobialtai mountain in the north,the Heihe drainage basin forms a mountain-basin complex in the inland arid area.The oasis belt distributed in the basin was developed with soil and water material resources from the mountains.Ejina oasis,located in the central part of the arid Northwest China,serves as an important ecological defense of the entire region.In the latter half of the20th century,the ecological sys-tem of the oasis was severely damaged,the original landscape structure was dramatically de-stroyed,the water supply from Heihe River was decreasing year by year,from1.225billion m 3 a year in the1950s to0.724billion m 3 a year in the1990s.The level of groundwater table was lowed and the land salinization were aggravated accordingly.The area of Populus euphratica and Elaeagnus angustifolia woods were decreased from34.5thousand ha to22thousand ha dominated with virgin forest.The scrubs of Tamarix ramosissima were decreased by50per cent,becoming the sparse and short community.The serious degrada-tion of herb meadows led to succession to Sophora alopecuroides community.In order to conserve the important ecological barrier of Northwest China,the main objective is to restore and conserve the natural oasis,increase the coverage of Populus euphratica woods,Elaeagnus angustifolia woods,Tamarix ramosissima scrub and Haloxylon ammodendron brush woods.Meanwhile,it is necessary to develop artificial grassland to improve the land coverage,and to construct the artificial-natural oasis.Water supply must be guaranteed for the conserva-tion and the restoration of the oasis.More attention should be paid to keep the groundwater at a suitable level,control the water-salt dynamics,and enhance the coupling effect of the bio-land-scape diversity.Thus,the ecosystem health and resource-environment safety of oasis can be com-pleted.