The corrosion laws and the mechanisms of Portland cement hardened paste and aluminate cement hardened paste in sulfuric acid and citric acid solutions were studied by analyzing the appearance change of mortar， measuring the mass loss rate and corrosion resistance coefficient of mortar in acid solutions combined with X-ray diffraction（XRD）， scanning electron microscopy （SEM） and elemental energy spectroscopy （EDS）. The results show that compared with sulfuric acid solution， citric acid solution has stronger corrosion ability for two cement mortars. Compared with Portland cement， aluminate cement shows better acid corrosion resistance， mainly because the hardened paste of aluminate cement contains a large amount of aluminum glue， which can neutralize more H⁺ in sulfuric acid solution and delay the diffusion rate of H⁺ to the inside of the hardened paste in citric acid solution.