Abstract: This paper studied the thermal decomposition characteristics of aluminous cement and Portland cement raw meal using thermal analysis and some other test methods. The decomposition heat of aluminous cement raw meal is 703.3kJ/kg and the heat of Portland cement raw meal is 901.2 kJ/kg. It was also researched that the decomposition activation energy(Ea) calculation of limestone and diasporite in two cement raw meal has also been calculated using the shrinking cylinder mechanism with surface reaction rate controlling, random into nuclear and the growth mechanism.