In order to make clear the characteristics of soil aggregate and fertility in irrigation silting soils affected by sediment input in Ningxia section of the Yellow River，sediments were dynamically sampled in May (spring irrigation)，August (summer irrigation)，and October (winter irrigation) in the main river；and in contrast to irrigation silting soils，the mechanical composition，mechanical stable aggregates and their nitrate，ammonium nitrogen，and available phosphorus contents were determined，respectively.The results showed that sediment aggregate of <0.25 mm accounted for 70.8%～87.5%；aggregates of >0.25 mm，mean weight diameter，and geometric mean diameter of sediment were showed as August>May>October，and its aggregates stability was significantly lower than that in the irrigation silting soils.Nitrate contents in different particle size aggregates of sediment accounted for 78.9%～99.3% of mineral nitrogen.Available phosphorus contents were even higher in aggregates of 1～2 or 0.5～1 mm in sediment. Mineral nitrogen contents in different aggregates between sediment of May/August and irrigation silting soils was positively correlated，but the correlation was negative in October.Available phosphorus contents in different particle size aggregates between sediment and irrigation silting soils was always negatively correlated.Therefore，sediment aggregates of <0.25 mm have a great influence on aggregate structure in the irrigation silting soils，and available nitrogen and phosphorus is the highest in different particle size aggregates of sediment during spring irrigation period in Ningxia section of the Yellow River.