Abstract: The thermal decomposition of H₂O₂ with different concentrations in the air was studied by C80 calorimetry.The effect of different heating rates on the thermal decomposition of H₂O₂，the activation energies of thermal decomposition，and TMRad（Time to maximum rate under adiabatic condition） were obtained by thermal analysis techniques.Results showed that the rise of heating rate could lift both initial and peak exothermic temperatures of H₂O₂ with various concentrations.The activation energy ranges of thermal decomposition of H₂O₂ with mass fractions of 27.5%，50%，and 70% were 51.05～94.30 kJ/mol，16.40～66.72 kJ/mol，and 32.50～76.15 kJ/mol respectively.Under 40 ℃（the maximum ambient temperature），TMRad corresponding to the each mass fraction of H₂O₂ were 26.16 h，6.74 h，and 5.73 h，respectively.

Key words: hydrogen peroxide, C80 calorimeter, thermal decomposition, activation energy hydrogen peroxide, C80 calorimeter, thermal decomposition, activation energy