The present study concerns a work on the investigation of the effect of the dehydration temperature on the dissolution process of a boron mineral, ulexite, in sulfuric acid solution. In the experiments, the dehydration temperature and dissolution temperature were chosen as the parameters. First, the dehydration of ulexite was performed isothermally in an oven, and DTA and X-ray analysis were carried out to observe the structural changes in the mineral. The effect of the dehydration temperature on the dissolution rate of ulexite in sulfuric acid solutions was then investigated, using a batch reactor made of glass. The kinetic parameters of the dissolution process, frequency factor and activation energy, were evaluated using dissolution data.