This paper puts forward a new kinetic model of potassium based on Lotka-Volterre model in ecology. A potculture experiment was conducted showing that with the model,dynamic trends could be simulated of readily available potassium and slowly available potassium of soil in the growing period of peanut.The test of potassium absorption indicated that the change in K absorption in different growing periods of peanut accorded with the Logistic model.From the above two models,constants of the maximum release rates for mineral K(Kmm),slowly-available K(Krm)and rapidly available K(Kam)could be got.Correlation analyses showed that the relationship was obvious of Kam with K absorption of the current crop,its biomass yield and its peanut yield,and between Krm and K absorption by the current crop.Therefore, Kam and Krm could be used as index of potassium release rates in soil.