Reactive dyeing is one of most widely used methods for the coloration of cellulosic fibers. Reactive dyes have a low utilization degree compared to other types of dyestuff, since the functional group also bonds to water, creating hydrolysis. Salting out crystallization process was used to obtain dye crystals from solution. Physical properties and growth rate were measured for the design of the crystallization process. Density of RB8 crystal was 1.92 g/cm^(3) and that of RB49 was 1.26 g/cm^(3). Density of dye solution was linearly decreased with rise in temperature. Saturation solubility to the water was constant over room temperature. Solubility of dye solution was decreased by higher temperature and higher KCl concentration. The growth rate of RB8 was 0.964×10^(-06)ΔC^(1.041) and that of RB49 was 2.922×10^(-06) ΔC^(2.236) respectively.