Abstract:Wild soybean is the progenitor of soybean, sharing the gene pool of soybean. In this paper structure and geographical distributions of the natural populations of wild soybean in Hebei Province were analyzed using some important quantitative traits. Coefficients of variation within populations were greatest for 100-seed weight (46 % ) followed by fat content (17 % ), flowering time (10.3 % ) and protein content (4.7% ). Within-population mean flowering times were related to latitudes, but 100-seed weight, fat and protein contents were not. Every population had some individual plants with outstanding differences in character performances that had virtually been caused by the accumulation of gene frequencies for quantitative characters. It was observed that there were different genotypes for genetic flexibility in flowering photoperiodic response, although the populations had always been subjected to the same photoperiodic induction. A similarity analysis of the natural populations indicated a relationship between the quantitative structures of populations and their geographic and ecological distribution areas--showing distinct ecological groups in wild soybean.