A hydroponic experiment was conducted to study the physiological response of rice plant to different light intensity after decreasing root/shoot ratio.Root system was placed in cylindrical nylon bags to cause root confinement.The diameters of the root bags were 3,4,(5 cm),respectively and the height was(25 cm).The results showed that under the same shading level,root confinement had no significant effects on the dry matter accumulation in the aboveground parts,but had significant effects on underground parts.The root mass and root/shoot ratio decreased significantly after root confinement,the smaller the root bag,the more the root/shoot ratio reduced.After shading,root and shoot dry matter accumulation,root volume,leaf chlorophyll content reduced significantly at heading and ripening stage.Under 70% shading treatment,the total surface area,active area and surface area per volume of the root system in(5 cm) treatment increased by 57.7%,26.0%,41.5% at heading stage,and the active area and percentage of active area of root system increased by 74.1%,58.2% at ripening stage compared with control.