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).