Abstract: Adiabatic theory and its application in evaluating thermal stability of energetic materials are studied. The improved equation for the rate of adiabatic temperature rise, initial exothermic temperature, and the time to attain maximum rate of temperature rise are presented. The effects of thermal inertia factor on the results of measurement of the adiabatic acceleration rate calorimeter are discussed. The thermal stability of RDX is studied by the acceleration rate calorimeter. The results show that the modified values have good agreement with calculated results on the basis of the improved model.