Mixed ester propellants are extensively used in artillery weapons due to their superior mechanical properties. This study investigates the decomposition kinetics and mechanism of mixed ester propellants using Differential Scanning Calorimetry (DSC) and Thermogravimetry-Fourier Transform Infrared Spectroscopy-Mass Spectrometry (TG-FTIR-MS). Kinetic parameters were determined via a model-free approach, while laser diagnostic technology captured radicals and molecular fragments during the decomposition-combustion process. Results indicate a single exothermic peak during decomposition, with apparent activation energy (Ea) increasing initially (0.01 ≤ α ≤ 0.4) and stabilizing around 278.43 kJ/mol later. The thermal decomposition behavior of mixed ester propellants follows the Sestak-Berggren equation, consistent with an autocatalytic reaction. NO2 generated during decomposition acts as a catalyst, accelerating the decomposition process. CN* radicals were detected throughout the combustion stages, indicating the resilience of the CN bond against breaking. This study can provide a theoretical basis for predicting fire development and for the selection or design of fire sensors.