This study is focused on the the crystallization kinetics of calcium sulfate dihydrate. The reactive crystallization of calcium sulfate dihydrate in the absence and presence of 250 ppm, 1000 ppm and 2500 ppm oxalic acid concentrations was carried out in a mixed-suspension-mixed-product-removal (MSMPR) type crystallizer. The growth kinetic of calcium sulfate dihydrate crystals was analysed in accordance with size-independent and size-dependent growth models. It was found that the growth rates of calcium sulfate dihydrate crystals depend on the particle size and the kinetic parameters were evaluated according to Bransom, MJ2, and MJ3 models. Also, the relative coefficient, mean square error and the mean square deviation were determined for each model and the results showed that MJ3 model was the best fitting model to the experimental data.