Abstract: The LISST-100X was employed to analyze 28 suspended sediment samples from the middle and lower reaches of the Lancang River, and the study investigates the correlation between grain size characteristics and fractal dimensions of the sediments. The results show that: ① The compositions of sediments rank from silt and sand, followed by clay, respectively accounting for 48.92%, 45.06% and 6.02%. ② The average particle sizes of suspended sediments decrease against the distance from their sources, meanwhile the average particle sizes of sediments in the reservoirs are bigger than those below the dams, but their sorting coefficients increase. ③ The fractal dimensions of suspended sediments range from 2.0017 to 2.5383. Meanwhile, the lg(W(r<x)) and lg(x)) are well fitted (R²> 0.92), so they have fractal features. ④ The fractal dimensions are linearly correlated (p<0.01) significantly with the volume percentages of clay, mean grain sizes, and sorting coefficients, with correlation coefficients being respectively 0.8568, −0.7962 and 0.7513. The results reveal the theoretical characteristics of suspended sediment grain sizes and fractals in Lancang River Basin, providing basic data for the management and control of water and sediment environment of the river.