The occurrence of green stem syndrome(GSS) of soybeans is increasing in Japan in recent years. Therefore it is needed to elucidate the cause of GSS and to find the cultivation method for reducing GSS in soybeans. Eight cultivars from different latitudes of Japan were planted in three sown date in 2003 and 2004, and three lines of supernodulating, nonnodulating and normal nodulating soybeans were planted in 2003. The half depodding treatment was applied at R5 stage. The degree of GSS (DGSS) was classified by the appearance according to Furuya and Umezaki (1993). There were positive correlations between DGSS and stem water content or stem nitrogen content in two years. DGSS was more severe with earlier sowing date and earlier maturing cultivars. The depodding treatment increased DGSS in general, however some cultivars with earlier sowing date showed opposite result. The depodding effect on DGSS seems to be more severe with less nodulating lines. We also tried to elucidate the effects of the half depodding treatment on photosynthate distribution in a plant and root hydraulic resistance with pot-grown plants. More photosynthate was distributed to the stem and root with a half depodding plants compared to the control plants. The decline of root hydraulic resistance during senescence was alleviated with depodding. It appears that higher photosynthate supply to the root and stem delayed its senescence, therefore depodding plants kept higher water absorption and then stem moisture at maturity. The cause of GSS in this experiments will be discussed.