The grain characteristic of falling dust and different height surface and their relationship were analyzed by the field observation data.The results are as follows: the falling sand-dust of 0.1 m height near surface is mainly from saltation matter,the fine sand compositions of falling dust are fewer and the powder sand elements are more.The relationships between the grain characteristics of surface and the sand dust storm are obvious,and the grain characteristics can reflect the degree of affording sand-dust from surface.