Plant root system is the channel of material exchange between vegetation and soil. In the loess hilly area with serious soil erosion and fragile ecology, it is great significance to deeply understand the influence of root system on soil physical and chemical properties. In this study, six plant species were taking as research objects, which were Bothriocheloa ischaemum, Carex lanceolata, Artemisia leucophylla, Artemisia gmelinii, Sophora viciifolia and Caragana intermedia. Roots and soil samples of 0-10, 10-20, 20-30, 30-40, 40-50 and 50-60 cm soil layers were taken. The root length density, root surface area density, mean root diameter, soil organic matter, soil bulk density and water stable aggregate content of each species in each soil layer were analyzed. The results showed that the roots of the species studied were mainly fine roots. In the 0-20 cm soil layer, the root length density of herbaceous plants was significantly higher than those of other species (P<0.05), which followed the order of B. ischaemum > C. lanceolata > A. leucophylla > A. gmelinii > S. viciifolia > C. intermedia, while the average root diameter was opposite. The root system could increase the SOM content in varying degrees, and the SOM content had a significant positive correlation with the root mean diameter and root surface area density(P<0.01). In the soil profile, the weight percentage of water-stable aggregate significantly decreased in the sample plots of B. ischaemum, C. lanceolata and A. sacrorum. The weight percentage of water-stable aggregates did not change significantly with depth in the sample plots of A. leucophylla, S. viciifolia and C. intermedia. Root surface area and root length density could significantly increase the weight percentage of water-stable agglomerates of 0.5~2 mm (P<0.05), which indicated that the root system could agglomerate small-size aggregates into larger-size soil aggregates. The above research results showed that root system could increase soil organic matter content and medium-size aggregate content, improve soil structure and soil stability, and played an important role in increasing soil corrosion resistance.