Nanocrystalline aluminium bulk material with average grain size of 25.2 nm was prepared by warm-vacuum-compaction method. The as-prepared nanocrystalline aluminium was characterized by X-ray diffraction (XRD), differential scanning calarmeutry analysis (DSC), thermogravimetric analysis (TG), and Microhardness test, respectively. The experimental results show that the average grain size and microstrain of the nanocrystalline aluminium are 25.2 nm and 0.018%, respectively. The melting point of as-prepared nanocrystalline aluminium is 918.9 K, which is lower than that of coarse-grained aluminium by 14 K. The endothermic value of nanocrystalline aluminium is 196.3J/g. The average microhardness of the as-prepared nanocrystalline aluminium is 1.65 GPa, which is 11 times higher than that of coarse-grained aluminium.