Grassland is an important part of terrestrial ecosystem, plant root system plays a critical role in the growth and development of the whole plant, which has the basic functions of storing nutrients, transporting water and supporting plant body. And root biomass is one of the important bases and parameters for studying grassland ecosystem. Thus, studying how root biomass of the grassland changes along environmental gradient is of great significance to local vegetation construction and restoration. Here, we selected ten sites from east to west in the Loess Plateau, which covered the main grassland types, including forest grassland, typical grassland and desert grassland. At each site, the roots of grassland plant were sampled to 0 cm to 50 cm soil depth at eight experimental plots (1m×1m) by using roots cores. We aimed to reveal the vertical distribution of root biomass of three different grassland types in the Loess Plateau, and explore the pattern of root biomass along the environmental gradients and their influencing factors. Our results showed that: (1) the root biomass of three different grassland types in the Loess Plateau was significantly different (P<0.05), with the root biomass of forest grassland being the largest and that of typical grassland being the smallest. (2) All of the root biomass vertical distributions of the three different grassland types in the Loess Plateau were "T" type, and the surface soil (0-10 cm) accounted for more than 55% of total root biomass. Moreover, more proportion of the root biomass of the desert grassland was distributed on the surface soil. (3) As the longitude increased, the grassland root biomass of the Loess Plateau decreased first, and then increased. However, the ratio of the root biomass of shallow soil layer to the root biomass of deep soil layer (i.e., shallow-deep ratio) did not show an obvious longitudinal pattern. (4) The change in total root biomass was affected positively by the mean annual temperature (MAT)(P<0.01). But the root biomass of deep soil layer was affected by both climate and soil nutrient content(P<0.01), and the shallow-deep ratio was influenced negatively by the total soil phosphorus of average soli layer and deep soil layer (P<0.05). (5) Climate and soil factors could explain 5.12-39.36% of the variation in root biomass, among the independent effects, climate factors had the largest explanatory degree to root biomass, which could reach 2.77%-9.12%.