The Crystallization kinetics of gypsum were measured in simulated Solutions of flue gas desulfurization. It was found that the growth rate of gypsum crytals (G) was related to the degree of the supersaturation (S) with the following relationship. G=1.05 S^1.48 Since the relationship is an exponential function with a degree higher than one, it is implied that the growth rate of gypsum crystals is dominated by the integration of solute ions rather than the diffusion.