In a stainless steel autoclave of 15 ml capacity, pure hexagonal aluminum nitride （h-AlN） foam has been synthesized by direct reaction of AlCl3 with NaN3 in non-solvent system at 650 ℃ for 3h. The scanning electron microscopy （SEM） shows that the obtained foam material has characteristic sponge-like morphology. The results of X-ray diffraction （XRD） indicate that the AlN foam has a pure hexagonal structure. The absorption spectra at various temperatures indicate that there is a relatively strong absorption peak at about 202 nm. The infrared absorption spectrum shows that the foam has two absorption peaks, centered at 1381 cm-1 and 730 cm-1 respectively. In addition, a possible synthesis mechanism for h-AlN foam is discussed.