Abstract: The leaching behavior of Cs⁺ in alkali-activated slag-clay minerals composite cement (AASCM) and ordinary portland cement (OPC) waste forms at temperatures of 25, 40, 70, and 90 ℃ was researched. The leaching mechanism was also discussed. The results indicate that the leaching behaviors of Cs⁺ in the AASCM and OPC waste forms are quite different. The cumulative leaching fractions (CLF) of Cs⁺ in the OPC waste form tend to be a same value at the four temperatures while the CLF of Cs⁺ in the AASCM waste form increase with increasing temperature. In the AASCM waste form, the state of adsorption/solid solution Cs⁺ is about 90% and the dissolution Cs⁺ is about 10%. The existent state of Cs⁺ in the OPC waste form mainly includes the solid solution Cs⁺ and dissolution Cs⁺, which are 40% and 60%, respectively.