To explore drought resistance characteristics of adzuki bean at the seedling stage, 235 adzuki bean accessions from different regions were subjected for drought resistance tests upon drought stress treatment by pot cultivation assay. The root morphology, plant height, biomass and canopy wilting were measured, and the statistical analysis was conducted using the subordination function method, principal component analysis (PCA) and cluster analysis. Under drought treatment, the taproot length, lateral root length, total root length, and ratio of shoot dry mass to root dry mass were higher than those of the control groups, but taproot surface area, lateral root surface area, total root surface area, taproot volume, lateral root volume, total root volume, shoot dry mass, root dry mass, plant dry mass and plant height were lower than those of the controls. The correlation analysis on the subordination function values of each trait showed the correlation with the total root surface area. The first three principal components explained 82.8% of the phenotypic variations at 15 traits. The first, second and third principal components were mainly contributed by root surface area, dry mass, and taproot length, respectively. These accessions were classified into three types, composing of drought-resistant, intermediate and drought-sensitive, which accounted for 8%, 63% and 29% of total accessions, respectively. According to the subordination function value, principal component analysis and root morphology of different types, the total root surface area served as a major index for the evaluation of drought resistance at the seedling stage. Moreover, 15 drought-tolerant accessions were identified being valuable for further drought-resistant breeding and gene mining in adzuki bean.