The EXP1 gene encodes expansin, which has the ability to loosen the plant cell wall. The soybean expansin gene GmEXP1 is activated specifically during the root elongation process, and thus it plays important roles in root development. During the drought period, changes in pressure within the cell and the fast development of the root allow plants to collect water from deep soil, which in turn helps plants grow and develop. In this study, we have successfully cloned and generated a GmEXP1 construct expressing recombinant expansin protein in tobacco plants. GmEXP1 is expressed in transgenic tobacco plants and passed on to the next generation. The transgenic tobacco plants have improved drought tolerance, which is demonstrated in both the length and volume of roots. From these promising results, we applied the same approach to generate drought-tolerant plants.