Abstract: The Pb-contaminated soils stabilized by alkali-activated GGBS and the mechanism are researched. The results show that the acid capacity value ascended with the binder dosage increases for the contaminated-soils stabilized by GGBS-MgO. The specific surface area of soils stabilized by GGBS-MgO is higher than that of uncontaminated soil as the Pb inhibites the hydration reaction of GGBS-MgO. The strength of stabilized soils with GGBS-MgO is higher than that of uncontaminated ones, which has a liner relationship with the specific surface area. The SEM and XRD results indicate that the main hydration products of stabilized contaminated and uncontaminated soil are C-S-H and Ht and can be analyzed using the XRD methods. The accumulative mercury and pore diameter results show that the accumulative mercury mass of the stabilized uncontaminated soils is higher than that of the contaminated soils stabilized by GGBS-MgO.