Root behavior and biomass changes of arid plant Sophora alopecuroides L. to the soil heterogeneity and competitors were investigated. We set 6 experimental groups (i.e. 3 soil treatments (homogeneous, patchcenter and patchedge) by 2 competition treatments (alone and with competitor)) with ten replicates each group. The results showed that: 1) the distribution and elongation of S. alopecuroides root had close relationship with competition. When S. alopecuroides grew alone, it adopted a broad rooting strategy regardless of the distribution of resource, indicating that resource distributions alone did not alter root placement. In contrast, competitors restricted root distribution. 2) Competitors also made the maximal breadth and distribution of the focal plants root change with the resource distribution. In uniform soil with competition, the roots of both the focal plants and the competitors distributed less in the overlapped region than those in the unoverlapped region; in the patchcenter treatment with a competitor, plant roots highly overlapped in the patch; in the patchedge treatment with competition, the focal plant got the abundant resource much easier and therefore most of the roots toward the center of box distributed in the range of ［7 cm, 11 cm］.