To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum (Co-B/Al) nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate (AP) and AP-based solid state propel-lants. X-ray diffractometry (XRD), scanning electron microscopy (SEM), inductive coupled plasma emission spectrometry (ICP), differential scanning calorimetry (DSC) as well as strand ber method were employed to characterize the crystal phase, morphologies, chemical com-position, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co_(72.6)B_(27.4)covers the surfaces of Al particles. Addition of the as-synthesized Co-B/Al nanocomposites as catalysts promotes AP decomposition, en-hances the bing rate, and lowers the pressure exponent of the AP-based propellants considerably.