Abstract: The variation features of crystalline shape and morphology of hydrate aluminum sulfate in the dehydration process by TG，XRD，SEM，and molecular simulation were investigated，and the theoretical data for alumina preparation from hydrate aluminum sulfate was offered.The dehydration was divided into three steps according to the transformation of crystal structure. In the 1st step（30~80 ℃），2.7 moles of water was dehydrated，and the structure belonged to triclinic system. In the 2nd step （80~322 ℃），12.65 moles of water was dehydrated，the structure belonged to monoclinic system.The 3rd stage occurred at 322~383 ℃ with 1.15 mole water loss，and the structure belonged to hexagonal system.Results of SEM and MS simulation showed that in the dehydration process，the crystal morphology transformed from flake-like to granular-like，and finally to flake-like again.The exposed surfaces of anhydrous aluminum sulfate were vertical to that of 17-hydrate aluminum sulfate.In the preparation of anhydrate aluminum sulfate from hydrate aluminum sulfate，obvious volume shrinkage occurred with breaking of granules.The dehydration of multi-crystalline hydrate aluminum sulfate is a potential way to prepare sand-like alumina.

Key words: aluminum sulfate, dehydration, morphology simulation, alumina