The expansive characteristics of new MgO-based expansive materials and the compensating shrinkage of cement paste with high C_3S content were investigated. The results show that the shrinkage of cement paste can be compensated by the new MgO-based expansive materials well, only if the burning temperature and burning time of expansive material are controlled and the dosage of expansive material in cement is suitable according to the hydration temperature and with fly ash or not.