Abstract: Desulfuration gypsum is a commonly used cement retarder, and accidents with abnormal cement setting time caused by the use of desulfuration gypsum often occur. By using experimental methods such as XRD, XRF, dissolution characteristic analysis, and DSC TG, the cause of abnormal cement setting time caused by the use of desulfurization gypsum in a certain enterprise was analyzed. The analysis results show that the presence of an appropriate amount of impurity ions in desulfuration gypsum has a certain improvement effect on the retarding effect of cement; desulfuration gypsum containing a large amount of hemihydrate gypsum has high activity, fast dissolution, high solubility, and fast retarder effect. Before using industrial by-product desulfurization gypsum in cement enterprises, relevant physical and chemical analysis should be conducted to optimize the addition ratio of desulfurization gypsum and stabilize cement quality.