High burning-rate composite solid propellants with fine ammonium perchlorate (fine-AP) and catocene have high mechanical sensitivities. The products of fine-AP and catocene mixtures after low-temperature exothermic reactions at about 173 degrees C were analyzed by X-ray photoelectron spectroscopy (XPS). The result showed that FeO, Fe2O3, or FeClx were generated during the oxidation of catocene in the fine-AP/catocene mixture. The mixture of fine-AP and catocene has high impact and friction sensitivities, whereas the impact sensitivity of the after-heated fineAP/catocene mixture reduced from 88 to 18% and the friction sensitivity also decreased from 80 to 66%. The low-temperature oxidation of catocene is one important incentive for the high mechanical sensitivity of fine-AP/catocene mixtures.