Grain size characteristics of aeolian sediments can provide lots of information about sedimentary environment and process,sediment transporting forces.This paper selected the semi-fixed and fixed dunes at Minqin County as research objects,and studied the sediment samples systematically using the grain size analysis method.The results indicated that fine sand is dominant in the semi-fixed and fixed dunes surface sediments,and the very fine sand follows;the grain size compositions of semi-fixed and fixed dunes are similar,but difference in contents of components can be detected.The mean diameters of semi-fixed and fixed dunes are 2.69 Φ and 2.66 Φ respectively with similar sorting and skewness features,showing nearly symmetrical distribution patterns when moderately sorted.The analysis of the grain size parameters showed that a quadratic polynomial relationship(R²=0.404 1) exists between the mean diameter and skewness,but insignificant linear correlation can be found among kurtosis and the mean diameter,the sorting feature,kewness show(0.550,0.496,0.356),and the sorting feature and the mean diameter,skewness are uncorrelated.