Abstract: According to the field experiments and the climate data in Sanjiang Plain wetland,the profit and loss of soil water in soybean field were analyzed.The results showed that the natural rainfall could meet the needs of soybean water consumption in normal years and the growth of soybean would suffer from water stress in arid season.The seasonal drought has taken place here frequently in recent years.So it is very important to study water balance and effective utilization of regional water resources.