It　is　of　great　interest　to　study　the　shape　effect　on　the　catalytic　activity　of　metal　nanocrystals,　which　exposed　different　crystallographic　facets　upon　adopting　various　shapes.　The　investigations　on　shape-dependent　catalysis　of　supported　metal　nanocrystals　need　to　be　conducted　over　nanocrystals　with　well-defined　shapes　and　cleaned　surface.　The　palladium　nanocrystals　with　cubic,　octahedral,　and　spherical　morphologies　were　synthesized　and　well　dispersed　onto　the　inert　silica　support　after　removing　the　capping　agents,　which　were　used　as　the　heterogeneous　catalysts　for　carbon　monoxide　(CO)　oxidation.　It　was　found　that　the　crystal　facets　of　Pd　nanoparticles　played　an　essential　role　in　determining　the　catalytic　oxidation　properties.　As　a　result,　the　octahedral　and　spherical　nanoparticles　that　predominantly　exposed　the　Pd　{111}　crystal　facets　exhibited　significantly　better　catalytic　activity　than　the　palladium　nanocubes　that　possessed　the　Pd　{100}　crystal　facets　as　the　basal　plane　for　the　CO　catalytic　oxidation.　It　was　inferred　that　the　appropriate　adsorption　strength　of　CO　molecules　on　Pd　{111}　planes　was　beneficial　to　the　enhancement　of　the　catalytic　activity.