The alkaliactive burned clay cement is a new kind of alkline cementitious material, so it is necessary to find out thermal stability of this material. This paper discusses principally the relation between strength of mortar of this material and the different temperature of heat treatment. Moreover, the thermal stability of this material is compared with the Portland cement. The characteristics of the thermal stability of these two materials have been explained based on the product of hydration and mechanism of hydration of these two materials.