Herein, kinetics extraction of platinum from spent auto catalysts, using nitric acid as an oxidant in hydrochloric acid solution, was investigated. The parameters such as temperature, hydrochloric and nitric acid concentrations, stirring speed, particle size and liquid/solid ratio, were analysed. The kinetic data were analysed using the shrinking core model. A variant of this model fits the kinetic data more appropriately. At a temperature of 90°C, the values of R2 in surface chemical reactions and diffusion were 0.819 and 0.937, respectively. With the alternative model, however, 0.991 was obtained. The activation energy for the dissolution was 35.75kJ/mol.