This paper aims to establish a mathematical model that can analyze the whole leaching kinetics process of ion-adsorption type rare earth ores. This leaching process is composed of three steps:(1) ammonium ions arrive at the ore particle surface through the diffusion layer;(2) ammonium ions exchange with rare earth ions; and (3) rare earth ions enter into the external solution through the diffusion layer. In the leaching process, it is hypothesized that the ore particle size remains constant. The process of ammo-nium ions and rare earth ions passing through the diffusion layer was described by the Fick law, and the reversible ion exchange process between ammonium ions and rare earth ions was described by the Kerr model. A leaching kinetics model of rare earth ions by ammonium ions was constructed. Accuracy of this kinetics model was verified with laboratory tests. It is found that the correlation coefficients of all data are greater than 0.9000. The proposed kinetics model is therefore feasible for kinetics analysis throughout the leaching process.