Overgrazing has severely degraded the grassland of Northern China causing serious loss of soil nitrogen (N). Along with the degraded steppe, Cleistogenes squarrosa will replace Stipa grandis, which was the original dominant species, to become the dominant plant in the community. In order to understand this transition, a study was made to examine the effect of N and selected functional plant groups on the rooting characterisitics of S. grandis and C. squarrosa. Two experiments were conducted in degraded grassland communities that were dominated by C. squarrosa.on the Xilingol steppe.on a degraded community. In Experiment 1 involved N addition along an increasing gradient (0, 10.5, 17.5, 28g N/m²) while in Experiment 2, two of three functional groups (high-energy, middle-energy and low-energy functional groups) were removed (1, 0, 0; 0, 2, 0; and 0, 0, 3) and adding N fertilizer(0, 17.5 g N/m²) in a factorial arrangement. After two years, the root length, diameter, area, and volume of S. grandis and C. squarrosa were measured using a Delta-T SCAN analyzer. Root response to N fertilizer as well as to the removal of functional groups, with two N levels, were analyzed. Under pressure from competition by other functional groups, the root length, area, and volume of S. grandis significantly increased under high N fertilizer (28 gN/m²) while root diameter and volume of C. squarrosa with 17.5 gN/m² were significantly higher than the other three N application rates. In Experiment 2, we did not detect a response in S. grandis to nitrogen addition(17.5 gN/m²)while removing functional groups but the root diameter of C. squarrosa increased significantly. In general removal of plant functional groups affects the root length and area of S. grandis and the root length, diameter and area of C. squarrosa. While the interaction between nitrogen addition and removal of plant functional groups affects the root diameter and volume of C. squarrosa, and it did not affect S. grandis.