The Grain for Green Project (GGP) has been implemented for 20 years in loess hilly-gully region on the Loess Plateau. To know the current situation of grasslands in the region is of great importance to select protecting approaches and choose regulatory restoration measures. 22 grassland communities in the Zhifanggou watershed in Ansai District were selected, and their classification, structure and the influencing factors were analyzed using Ward clustering and non-metric multi-dimensional sequencing (NMDS) methods. Results showed that:(1) 23 families and 83 species of plants appeared in the basin, among which the importance values of Gramineae, Leguminosae and Compositae accounted for 75%-85%. Grasslands can be divided into five associations:Setaria viridis association, Artemisia capillaris association, Glycyrrhiza uralensis association, Artemisia sacrorum association, and Bothriochloa ischaemum association. The vegetation coverage, above-ground biomass (AGB), below-ground biomass (BGB) and root:shoot ratio of S. viridis ass were significantly lower than those of the other four communities, but the Shannon-Wiener index and Pielou dominance index were significantly higher than those of B. ischaemum ass and A. sacrorum ass. There were no significant differences in AGB, BGB, and diversity index between A. capillaris ass, G. uralensis ass, and A. sacrorum ass.(2) Functional groups had significant effect on community structure, and short Leguminosae had significantly positive effect on the AGB and BGB, while tall Gramineae had a significantly positive effect on BGB, and short Asteraceae had significantly negative effects on both coverage and BGB.(3) Soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) content were all relatively low (6.21, 0.82, and 0.53 g/kg, respectively). The SOC and TN significantly affected species composition, functional groups and structural characteristics. In general, the grassland in the Zhifanggou watershed recovered well, and subsequent regulation measure selection should consider the types of grassland community and the differences in soil carbon and nitrogen contents.