Abstract: "Sandstorm" in Beijing should be classified geologically as "dust-storm", more accurately as "salt dust", containing quantities of saline (water-soluble salt materials). It has aroused widespread concern due to its posing a serious threat on human health and economic development. This study aims to provide new evidence for Beijing "salt dust storm" origin by investigating the source region including the south-eastern Mongolia, central Inner Mongolia, and western Hebei Province for physical and chemical properties of topsoil and some dust. Systematic topsoil was sampled in different sources of land sand, landform types, including agricultural land, sandy land, degraded grasslands, abandoned land (named after "farmland etc." in the following) and the desert Meanwhile dustfall was also collected from Beijing and some areas of sand source. The samples were analyzed for water-soluble salts and cation-anion concentration, pH, artificial and laser particle size, the proportion, and wind speed generating dust. The results show that the dried salty lake is featured by its high percentage of the <200 dust materials, water-soluble substances and some cation-anion ions such as Na+, Cl-. Its high pH, very tiny particle size, large specific surface area, low proportion and low wind speed generating dust, are well correlated with dustfall features of Beijing and of cities and towns near dust origin, while these features are different from those of the desert, sand, beach, agricultural land, abandoned land, degraded grass, etc.. This implies that dry salt lake basin area could be one of the most important and key sources of Beijing "salt dust storm". The soluble salt content, particle size, pH, proportion and wind speed generating dust could be considered as key indicators to determine the source of Beijing "salt dust storm".