Modification of Phosphogypsum and Its Application for Cement Retarder Yang Shuzhen Song Hantang Yang Xinya Zhu Jiaoqun Prof.,Center for Material Reseach and Analysis,WUT,Wuhan 430070,China.The composition and the structure of phosphogypsum, which its harm to cement was investigated, have been determined. Modificated phosphogypsum with excellent properties was obtained for cement retarder. The preparation process of modificated phosphogypsum was also presented in the paper.phosphogypsum;\ modification; cement retarder