Ca2+ transfer in the carbonation system of CO2-NH4OH-CaSO4 center dot 2H(2)O-CaCO3 is a complex multiphase mass transfer and reaction process. In this study, a kinetic model involving CO32- formation, CaSO4 center dot H2O dissolution, and CaCO3 crystallization was designed to describe the transfer. A gypsum disk was adopted as a raw material for dissolution, and Ca2+ concentration was measured to determine the unknown kinetic parameters. The model was experimentally validated in a semibatch stirred reactor. A multistep transfer route from Ca2+ to CaCO3 via NH2COO- and CaCO30 ion pair intermediates was described and divided into two parts by a ratio lambda, which was defined as the relative net accumulated rate between total dissolved calcium and carbon. When lambda > 0, NH2COO- hydrolysis controlled the transfer in the induction and nucleation periods. When lambda < 0, the dissolution of CaSO4 center dot 2H(2)O became dominant in the growth period. According to the rate-limiting steps, Ca2+ transfer could be affected by the CO2 flow rate and the impeller speed in different periods. Furthermore, as the impeller speed increased, the turbulence intensity was enhanced. As such, the nucleation rate was high, and the CaCO3 particles were small.