Tamarix chinensis sand dunes are specific bio-geographical landscape in Gurbantunggut Desert, which play an important role in maintaining the stability of regional ecological environment. Based on field investigation and indoor analysis, the soil grain size characteristics of 0—500 cm soil layer in T. chinensis sand dunes in the southwest of Gurbantonggut Desert were analyzed. The results showed that: (1) Soil grain size composition of T. chinensis sand dunes was dominated by silt and very fine sand, and the content was more than 80%, furthermore, the content of soil particle below 50 μm accounted for more than 57%. (2) With the increasing soil depth, the content of clay and silt, average particle size and sorting coefficient showed the trend of increase-decrease-increase. In general, the content of very fine sand and fine sand,skewness and kurtosis showed the trend of decrease-increase-decrease. The overall sorting ability of soil was poor. Kurtosis was generally mesokurtic peak, and the grain size distribution was positive skewness. The fractal dimension and average particle size were significantly positively correlated with clay and silt, and negatively correlated with very fine sand and fine sand, indicating that fractal dimension and average particle size could better reflect the characteristics of soil particle size composition of T. chinensis sand dunes. (3) Soil particle size of T. chinensis sand dunes was affected by soil water content, pH, total phosphorus, organic matter and electrical conductivity. The average particle size and fractal dimension could well reflect the characteristics of soil particle distribution in the profile of T. chinensis sand dunes, and soil grain size composition of T. chinensis sand dunes was a potential material basis for soil formation in the desert-oasis transition zone.