Soybean, which provides abundant proteins and edible oil, is an important crop; however, it is very sensitive to flooding stress. The growth and grain yields of soybean are seriously reduced by flooding stress. To explore the initial flooding-tolerant mechanism of soybean, flooding-tolerant mutant line and ABA treated soybean were used. Because both material and treatment showed the flooding tolerance, the commonly changed proteins in plants under initial flooding stress were identified. To identify the common proteins, gel free/label free proteomic technique was used.