In this study, the ultrasonic spray drying technology was applied to prepare composite microspheres of catalyst (Ta-Fe, Ph-Fe) and AP. The surface morphology of the two composite microspheres was characterized by scanning electron microscopy (SEM). Their particle size distribution characteristics were tested by a nano laser particle size analyzer. The results showed that the spray drying technology can uniformly compound the AP and the catalyst into spherical particles. The thermal decomposition process of Ta(Ph)-Fe/AP composite microspheres were tested by differential scanning calorimetry (DSC). The DSC data demonstrated that Ta(Ph)-Fe/AP composite microsphere had a very good catalytic effect and significantly promoted the thermal decomposition process of AP. In addition, the catalytic mechanism was discussed by calculating the change in activation energy. Compared with the raw AP, the activation energies of the Ta-Fe/AP and Ph-Fe/AP composite microspheres were reduced by 18.5 kJ/mol and 28.1 kJ/mol, respectively.