Taking soil degradation into account, Fuzzy comprehensive evaluation was adopted to construct prediction model of soil alkaline desertification in Xinjiang, and southern Junggar Basin was chosen as study area. Soil salt content, groundwater depth, clay content, organic matter, alkali-hydrolysable nitrogen, rapidly available phosphorus, rapidly available potassium, and pH value, were selected as assessment indexes. Risks of soil degradation were comprehensively assessed according to the prediction model in the study area. The results obtained indicated that there were different ranks of risk that increased from south to north in this area; moderate, high and middle-high risks were major parts and separately took up 46.56%, 23.01% and 20.59% of the total area, at the same time low and sky-high risks occupied very small part. The results of assessment could provide theoretical value on instructing local agricultural production and reasonable utilization of soil resources.