The variation of fertilizer-N in rice rhizosphere was studiedied means of the dense root plane in contact with soil blocks labelled by 15N and fresh frozen sections.Meanwhile some conditions of research method were determined.Results revealed that there existed a depletion zone of nitrogen in rice rhizosphere which was induced mainly by the decrease of fertiliter-N.The extension of depletion zone in soil was consistent with the rate of depletion.There was a exponential correlation between the rate of depletion (y) and the distance from root plane (x) in accordance with the equation y=a+bx^1/2,The content and depletion rate of fertilizer-N in soil varied with the cultivated time of rice.The amount of depletion in the rhizosphere soil of upper part of roots (below root node 4-6 cm) was greater than that of the lower part of roots (below root node 8-10 cm) due to the upper part of roots with more vigorous branches and higher ability of nitrogen absorption.In addition,raising temperefute during the growing period of rice promoted the rate of nitrogen uptake by root system and expanded the extension of depletion zone of fertilizer-N in soil.Therefore increased supplying capacity of nitrogen in soil to a certain extent may reduce the rate and extension of depletion of fertilizer-N in rhizosphere soil.Experiment showed that nylon cloth (pore radius<25 μ)and cellulose micropore membrance (pore radius<2 μc)were ideal materials for separation between the soil and root interface.These materials can allow water and nutrients to pass the membrance freely,but prevent the roots penetrating into soil.