Abstract:In order to analyze the relationship and difference of hydrological function of the stands structure in the loess hilly regions of southern Ningxia, the characteristics of understory herb biomass and biodiversity, canopy rainfall redistribution, forest understory evapotranspiration and soil moisture were studied in three typical forest stands (Armeniaca sibirica pure forest, Armenia sibirica-Caragana korshinskii mixed forest, Armeniaca sibirica-Hippophae rhamnoides mixed mixed forest)located in Pengyang County during the growing season in 2017. The results were as follows:(1) The order of stands surface coverage was A.sibirica-H.rhamnoides (0.81) > A.sibirica-C.korshinskii (0.71) > A.sibirica (0.67), the aboveground biomass of herbaceous plants followed the order of A.sibirica- H.rhamnoides (0.86 t/hm2) > A. sibirica(0.62 t/hm2) > A. sibirica-C. korshinskii(0.41 t/hm2), and the herbaceous plant biodiversity was followed the order of A.sibirica-C.korshinskii > A.sibirica-H.rhamnoides > A.sibirica. (2) The canopies of the three stands were relatively sparse, and the rainfall penetration rate were all greater than 90%,and the penetration rainfall was linearly correlated with the rainfall outside the forest,the stemflow and the canopy interception were logarithmic related to the rainfall outside the forest. (3) The seasonal variation of forest understory evaoptranspiration was "single-peak type", and the size of forest understory evapotranspiration during the research period was followed the order of A.sibirica-H.rhamnoides (245.0 mm) > A.sibirica (227.7 mm) > A.sibirica-C.korshinskii (220.9 mm), among them, the intermonthly variation of A.sibirica-C.korshinskiiwas the minimum. (4) The soil moisture in the middle and upper layers (0-80 cm) basically showed decreasing trend during the growing season, while the deep soil moisture showed the opposite trend, and the difference in the deep soil moisture was showed as A.sibirica > A.sibirica-H.rhamnoides > A.sibirica-C.korshinskii.In the severe erosion and drought-stricken loess region, when restoring stable vegetation with water and soil conservation as the main function, it was necessary to consider the effects of vegetation allocation patterns on surface cover and herb biomass and species diversity, as well as to consider the effect on soil moisture.Therefore, it is recommended to choose A.sibirica-H.rhamnoides mixed forest and A.sibiricapure forest in the vegetation restoration.