Abstract: By experiment of subsurface drip irrigation, the parameters of soil water, root system, dry bio-mass of corn and its yield of kernel at different growth stages during whole growing season were measured. From these data, the movement and redistributing rule of soil water, its influence on the root system and yield of summer corn were analyzed. The results are helpful to find the relationship with each other and to study water-saving mechanisms in subsurface drip irrigation. The mathematical model of root water absorption was established. Test results showed that subsurface drip irrigation was an economical irrigation technology. It could change the influence of soil moisture on quantities of root system, dry bio-mass of corn and its yield of kernel by controlling irrigation water supply accurately. In this way, it could maintain a balance of energy and reach an excellent ratio root to canopy mass.　At the same time, it enhanced water use efficiency and corn yield.