In the processing of uranium ores, the uranium is recovered from mill leach solutions by precipitation as yellow cake concentrates. Among the different existing processes, the continuous precipitation with hydrogen peroxide in a fluidized bed leads to high-quality solid particles. This paper deals with the determination of the crystal growth mechanism and the kinetic parameters. An experimental study is performed in a stirred batch reactor over a wide range of experimental conditions. The experimental method adapted to the uranium peroxide crystal growth study consists of following hydrogen ion concentration. In order to determine the kinetic parameters, a solubility model has been developed and the calculation of the supersaturation ratio is developed in this article. The deviation from ideality is taken into account and the activity coefficients are calculated by the Specific Interaction Theory. This article gives the results obtained for the uranium peroxide solubility, the supersaturation ratio calculation and crystal growth kinetic law. The treatment of the experimental data shows that the crystal growth rate corresponds to the dislocation mechanism.