By combining indoor pot experiment and scouring of undisturbed soil, three treatments were set up, i. e. bare land(CK), low planting density Lolium perenne L.(H1), and high planting density Lolium perenne L.(H2), to study the changes of soil physiochemical properties and root system at different growth stages. Soil anti-scourability of the growing grass and its relationship with influencing factors in loessial soil area were analyzed. The results showed that：(1) Soil bulk density, organic matter content, and water stable aggregate of CK fluctuated at four growth stages, but the range of changes were small. Soil bulk density decreased, organic matter content, water-stable aggregate, root surface area density (RSAD), and root weight density (RWD) showed an increasing trend with the extension of the growth cycle of H1 and H2. The RSAD of H1 and H2 treatments decreased with increasing root diameter at four growth stages. (2) Soil anti-scourability index (ASI) of CK and H2 were not significantly different at four growth stages. The ASI of H1 showed an increasing trend with the extension of growth time, and the effect of H1 treatment on ASI was the most significant at the16th weeks. (3) ASI had a diminishing power function relationship with soil bulk density. ASI had an increasing power function relationship with organic matter content, and water-stable aggregate. ASI had an increasing exponential function relationship with RSAD, and RWD. (4) There was no significant different between ASI and bulk density, water-stable aggregate, and 1.0 mm to 2.0 mm, 2.0 mm to 5.0 mm, and ＞5 mm diameter class RSAD. There was a significantly positive correlation between ASI and organic matter content, RSAD, and RWD (p＜0.05). There was a highly significantly positive correlation between ASI and ＜1 mm diameter class RSAD (p＜0.01).