In this paper, the ion-exchange kinetics of ion-exchange fiber has been studied, Under Finite Solution Volume (FSV), not only the effect of temperature, speed of stir, concentration and Ph value of the solution on the heterophase isotope exchange has been investigated, but the analytical solution of the exchange equation have also been obtained. By use of these solutions, the intraparticle diffusion coefficients D and the film transmitting coefficients D/delta under different conditions were calculated. Meanwhile, the reason why the ion-exchange rate of fiber is much faster than that of conventional spherical resins was also given with a proposed mechanism.