Abstract: The equations of solute rejection and solution permeation flux of multi-solute solution on porous membrane were derived on the basis of the adsorption-diffusion model. The physical significance of parameters in the equations was discussed. From the equations of solute rejection and solution permeation flux on porous membrane, the following conclusions were reached: when the solvent was adsorbed preferentially on the membrane surface, solute rejection could decrease as the membrane porosity increased;when the solute was adsorbed preferentially on the membrane surface, three curves of solute rejection vs. membrane porosity were obtained;solute rejection could decrease as membrane porous rate increased;a minimum value was shown on the curve of solute rejection vs. membrane porous rate; a min value and a max value was shown on the curve of solute rejection vs. membrane porosity.The solution permeation coefficient depended on the solute diffusion coefficient and diffusion selectivity of solute with solvent in the membrane phase.Membrane fouling was caused by the fact that the solute was adsorbed preferentially on the membrane surface, leading to increased membrane surface resistance and decreased solution permeation coefficient.