The work presents the results of mass crystallization kinetics experiments during the process of calcium ions precipitation from aqueous solution with the use of ammonium dihydrogenphosphate NH4H2PO4 under alkaline conditions (pH = 9). Experiments were carried out in the continuous laboratory DTB MSMPR crystallizer. The kinetic parameters of the process were evaluated after fitting the theoretical Crystal Size Distributions employing Rojkowski hyperbolic SDG model to experimental data.