SIWA Oasis is a depression located 450 km west of Nile ……...valley, 95 km east of the Lybian borders. It is the farthest from the Nile valley.  It is called “Amoun Oasis", and represents the last virgin Oasis in the Western Desert of Egypt. Decision Supporting System DSS - SLM model was used for sustainability assessment on the basis of “An International Framework for Evaluating Sustainable Land Management FESLM". The five FESLM pillars used are: productivity, security, protection, economic viability and social acceptability; assessed under the umbrella of bio-physical and socio-economic conditions through questionnaires held with land-users. The mapping unit OB showed the highest sustainability index followed by mapping unit DB (0.27 and 0.15, respectively). Mapping units OB and DB were short of meeting sustainability requirements (class III). The remaining mapping units have zero value of sustainability index; due to management practices which did not meet sustainability requirements (class IV). Four strategy scenarios were identified for land use (agriculture, industry, tourism and housing). Soils are suitable for tolerant and semi-tolerant plants, tolerant: date palm or olive trees, because they have salinity resistance. Land users cultivate crops of high profits such as cash crops vegetables (as tomato and onion), field crops (as alfalfa) and orchards (as olive trees, date palms, guava and citrus). Olives showed the highest profits followed by date palms achieving high benefit/cost ratio of 1.88 and 1.86, respectively.