Abstract: The adsorption and desorption experiment with low concentration silicon and pot experiments were conducted on seven paddy soil in different pH, and the relation between silicon supplying capacity and the parameters of adsorption isotherm were studied. The results showed that, In low silicon concentration conditions, the linear equation, which was found to be more suitable in describing silicon adsorption characteristics of soil. There are very significant linear positive correlations between value and rice relative yield or relative silicon content in plant. Therefore, value can be an index for assessing silicon -supplying capacity in paddy soil in different pH.