In order to compare the adaptive strategies of Stipa species,divergences of root traits and their relationships with the environmental factors were addressed along a large-scale gradient (>1600 km) in temperate grasslands from northeast Inner Mongolia to central Ningxia (106.88°-120.12° E,38.02°-49.35° N). Root traits (e.g. root biomass,root shoot ratio (R/S),anatomical structures and physiological adjustments) of seven Stipa species were measured twice over the growing season (dry season and rainy season) in eight sites along the gradient. Root drought resistance traits for Stipa species were enhanced or complicated with the decrease of precipitation along the gradient from northeast to southwest,resulting in divergence of adaptive strategies to moisture changes (or dry season and rainy season) for these Stipa species. In general,root biomass of Stipa species exhibited fluctuating growth trend among the eight sites,reflecting both interspecific differences and convergent adaptability to drought. R/S of Stipa species were greater in dry season than in rainy season,but its changing trend was not inconformity in the two seasons. The variations of root epidermal thickness (E_pt) and cortical thickness (C_ort) for Stipa species were consistent with root diameter (R_d) in the eight sites,but differed between dry and rainy seasons. E_pt and C_ort become thinner with the decrease of precipitation in dry season,this was in favour of water absorption and horizontal transportation. Thickening E_pt and C_ort in rainy season prevented water flowing back from stele to C_ort and enhanced water retention. Root proline (Pro) and soluble sugar (SS) contents of Stipa species in deep soil layer were significantly higher than those in the surface soil,mainly because the deep roots were newborn absorbing roots with strong physiological activity and the main participants in osmotic regulation. The comprehensive analysis showed that the growths of Stipa baicalensis,S. grandis and S. krylovii (in Duolun site) were restricted by the seasonal drought,and these species were highly sensitive to moisture with rapid biomass accumulation in rainy season. Drought resistances for some species (e.g. S. glareosa,S. breviflora,S. gobica,S. bungeana) was raised by increasing R/S,water retention and absorption capacities and accumulation of osmotic adjustments. Partial regressions exhibited that the root traits were related significantly with precipitation and altitude in the grassland region. The distribution ranges of Stipa species with complex adaptability,such as S. glareosa and S. krylovii,may expand,if the drought in the region intensified in the future as IPCC predicted.