Abstract: The selenium equilibrium in solid-liquid system of soils sampled from different natural zones in China and the Se-uptake of plant in culture experiment are studied, 1.The distribution of selenite-Se in solid-liquid System of soil conforms to the Freundlich equation and to the Langmuir equation in a great extent.The Se-absorption capacity in solid phase of soil(b)relates directly with content of R₂O₃ in soil and the apparent dissociation constant(K_c)is raised with pH,The distribution of Se effected also by the redox potential (Eh)as a factor influencing the stability or reduction of Fe(OH)₃,also as a factor controlling the valence aspects of Se in soil.The lowering of Eh caused by submerged condition may promote the reduction of Fe(OH)₃ and the decomposition of Se-R₂O₃ complex for acid soils,by which Se content in the soil solution is raised,and Se may be reduced for alkaline soils.The result is that Se content in the soil solution is reduced,The effect of organism in soil is complex,but it may be mainly on the proportion of active Self total Se in soil. 2.The significant retationships between Se content in the experimental plant and that in the soil solution,between change of the plant-Se and change of soil solution-Se when culture conditions are changed,which is found in this study,indicate that mass flow is a main way for Se-transport in soil-plant system,but the proportion of Se intercepted by plant roots is raised with quantity of Se uptaked by plant. 3.The uptake of Se reached to roots surface is inhibited by higher pH and indicates that Se-uptake by plant is a initiative procedure depended on the energy metabolism. 4.The culture in submerged condition of soil is advantatgeous to the transport of Se from stems and leaves to grain.