Non-uniform suspended load sediment-carrying capacity is the key issue in current research of suspended sediment transport and channel evolution. Experimental study on non-uniform suspended sediment-carrying capacity under low sediment concentration conditions is carried out in a sloping flume equipped with precise instruments and non-uniform suspended total sediment-carrying capacity and its grouped sediment-carrying capacity are calculated. The distribution law of grouped sediment-carrying capacity on sandy riverbed under different hydrodynamic conditions is analyzed according to the test data.The results show that there is a good positive correlation between the change of longitudinal gradient and bed material coarsening. The correlation coefficient of sediment-carrying capacity formula obtained by using the median particle size of bed material to determine characteristic settling velocity is relatively high. The reason for the inconsistency between upstream sediment grading and sediment-carrying capacity grading is due to the short recovery distance of the coarse particles in the suspended load，leading to deposition and a certain extent recovery of fine particles along the channel. Under the same hydrodynamic conditions, the coarse-grained sediment-carrying capacity gradation is mainly affected by changes in bed material composition, while the correlation between the fine-grained sediment-carrying capacity gradation and changes in bed material composition is poor.