The study was conducted at the Siziwangqi Agriculture and Animal Husbandry Academy Base in Wulanchabu of Inner Mongolia. The stocking rate test used a completely randomized block design, which is included contrast, light stocking rate, moderate stocking rate and high stocking rate in each of three blocks, and four precipitation gradients were randomly set in each stocking rate test area: natural precipitation, 50% reduced, 50% increased and 100% increased. The simulated precipitation test and the stocking rate test based on the different stocking rate tests of Stipa breviflora desert were carried out to analyze the corresponding characteristics of the aboveground and underground biomass of the plant on the stocking rate and precipitation and the results have been showed that:（1）the number of plant species in S. breviflora desert based on 4 species of stocking rates in 50% increased precipitation was significantly higher than that of 50% reduced precipitation (P<0.05), but it was no significant difference with 100% increased precipitation, (P >0.05) and in light stocking rate, the number of species in 50% increased precipitation was the most; （2）The aboveground biomass of 50% increased precipitation in light and moderate stocking rate was significantly higher than that of 50% reduced precipitation and environmental rainfall, but it was not different with 100% increased precipitation (P＞0.05). Whereas, precipitation did not lead to significant changes in the amount of aboveground biomass (P<0.05) in the enclosure and the heavy stocking rate; （3）With the increase of stocking rate, the root stock decreased gradually as the depth of the soil layer increased, increased water content also reduced the amount of root stock; （4）There was a significant positive correlation which has been shown as a linear function between root exudates and aboveground biomass（r=0.92，P<0.01）.