The conversion of hexabenzylhexaazaisowurtzitane (HBIW) to 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12- hexaazaisowurtzitane (TADB) is the major challenge in the production of hexanitrohexaazaisowurtzitane (HNIW) which only proceeds over supported palladium catalyst in a reductive debenzylation reaction. The catalyst is quickly deactivated during the debenzylation reaction. In this study, the change in Pd content in the catalyst during the reaction was measured. It was demonstrated that a portion of the palladium particles in the catalyst was leached during the reaction. The H-2 chemisorption isotherm on the catalyst at 303 K showed that the volume of chemisorbed H-2 on spent catalyst was significantly less than that on fresh catalyst. The N-2 physisorption isotherm on the catalyst at 77 K revealed that the surface area of spent catalyst was less than that of fresh catalyst. Moreover, the FESEM-EDS and TEM images and also wide-angle XRD patterns demonstrated that the mean sizes of palladium crystallites and particles in spent catalyst were larger than those in the fresh catalyst. These results demonstrated that the leaching of palladium particles and the aggregation of palladium particles in catalyst play active roles in the deactivation of catalyst in the debenzylation of HBIW.