Abstract: The pot experiments were conducted for two years to determine some characters of root system of wild soybean (Glgcine Soja). The results showed that there were significant differences among the genotypes of wild soybean in dry weight, morphological characters, growth vigor, formation and N-fixing activity of root nodules. The shoot/root ratio for wild soybean was increased during the growing period. The increment of root dry weight of wild soybean was much higher than that of cultivated soybean during the pod-bearing stage. The intensity of biological oxidation of a-naphthylamine in root system, the nodule number and N-fixing activity of wild soybean was higher than that of cultivated one during seedling stage. The taproot of wild soybean played an important role on nitrogen fixation during the seedling stage, but the lateral roots gave more nodules and higher N-fixing activity after stem-branching stage. The dry weight of top part and N content in leaves of wild soybean increased with the increases of root dry weight, number and fresh weight of nodules, and N-fixing activity. Abundant resources of wild soybean with high N-fixing activity and growth vigor of root system could be selected as the parent materials for soybean breeding.