The experiments of sulphur absorption characteristics of limestone particles have been carried out in an experimental equipment and TGA.A model used to simulate the process in which the calcina-tion and sulphur absorption reactions of limestone occured simultaneously was analyzed and established.Masss transfer coefficient α_(co_2) and diffusion coefficient D_(CO_2) of CO_2 through the calcined CaO were obtained by regressing the test data.The rationality of the model was examined by making comparison between the calculated values of model and the experimental results.