Pure　Al　nanocrystalline　bulk　with　high　relative　density,　small　grain　size　and　homogeneous　grain　size　distribution　was　prepared　by　combing　the　hydrogen-arc　condensation　and　spark　plasma　sintering　in　an　entirely　closed　system　filled　with　the　inert　gas.　It　shows　that　in　the　Al　nanocrystalline　bulk　structure,　the　nanograin　boundaries　are　clean　without　any　other　phases.　The　measured　mechanical　properties　of　the　Al　nanocrystalline　bulk　show　that　the　micro-hardness　has　a　value　of　2.12GPa,　which　is　about　6　times　higher　than　that　of　the　polycrystalline　bulk,　while　the　elastic　modulus　increases　only　a　little　as　compared　with　the　polycrystalline　bulk.