Hydrogen peroxide (H2O2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H2O2 mixed with sulfuric acid (H2SO4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T 0), heat of decomposition (ΔH d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H2SO4, the experimental data of T 0, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H2O2 and H2O2 mixed with H2SO4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.