In this work, preparation, characterization, and catalytic activity of Co3O4 nanoparticles (NPs) are reported. Co3O4 NPs was successfully prepared using Andrographys paniculata leaves extract (APE) as a weak base source and capping agent. Characterization was conducted using Fourier transform-infrared (FT-IR) spectroscopy, x-ray diffraction (XRD), energy dispersive x-ray (EDX), and transmission electron microscopy (TEM). According to FT-IR result, there were two main absorption peaks which corresponded to Co (II)-O and Co (III)-O bond at the wave number of 664.49 and 569.01 cm-1, respectively. XRD pattern confirmed that Co3O4 particles were theoretically hexagonal with nanocrystals form. EDX analysis revealed that Cobalt and Oxygen were the main atomic content on Co3O4. The formed Co3O4 NPs has particle size of approximately 20 nm. The catalytic activity of Co3O4 NPs was tested towards thermal decomposition of ammonium perchlorate (AP) by measuring differential scanning calorimetry (DSC). The temperature decrease on thermal decomposition of AP was found to be 157 °C at temperature range of 463 and 306 °C with decreasing of activation energy from 60.43 to 36.28 kJ/mol.