Abstract: The distribution and characteristic of soil salinization in topsoil(0cm-30cm)and its major causes were studied in Weigan River Basin with a combination of methods statistics, GIS and RS. The results revealed that: ①the area of the saline cultivated land is 11.48×104 km2, accounting for 39.83% of the tota1 area of the Weigan River Basin. The soil salinization phenomenon is common, especially in the lower parts of diluvial fans， middle and lower reaches of rivers, gentle low-lying topography, etc. The saline cultivated land takes the shape of strips and the shape of piece in the oasis marginal zone, and there is interleaving of heavy saline cultivated land with light and moderate saline cultivated 1and. ②Soil in the Weigan River Basin is mostly alkali soil with a pH of 8.42, and is high in salt content. Salts in the 0 cm -30 cm surface layer can reach 19.28g/kg on average. The main types of soil salinization are sulfate and chloride salts. ③Soil salinization is the product of combination of natural factors and human factors in Weigan River Basin. Natural conditions are the material basis for the salinization, and human activity is the driving force for the formation and development of secondary soil salinization in Weigan River Basin.