Abstract: Slag, lime, cement and gypsum were used as the cementitious agents to prepare the cementitious agent/soil composites. The hygrothermal properties of the cementitious agent/soil composites were investigated by guarded hot plate method and isothermal absorption and desorption method. The test results present that both cementitious type and content have significant effect on the hygrothermal properties of the cementitious agent/soil composites. Hygrothermal properties of the cementitious agent/soil composites were comprehensively analyzed by normalization method, the results show that 10% gypsum/soil composite has the best hygrothermal comprehensive property. The reason is that a mesh structure, which provides a structural supporting in the matrix, is formed by hydration of gypsum. The pores, which existe in the mesh structure, decrease the thermal conductivity of the cementitious agent/soil composites and increase the absorption property.