boehmite (alooh) was synthesized by sol-gel method. the physicochemical process and phase transformation of alooh during thermal treatment were investigated by the simultaneous thermogravimetric analysis, n-2 adsorption-desorption and in situ x-ray diffraction techniques. upon heating, alooh lost the physicsorbed water first, the chemisorbed water was desorbed at 210 degrees c, and the dehydroxylation was occurred at 310 degrees c. in the process, since the water was gradually lost, the bet surface area and total pore volume increased. the orthorhombic alooh transformed to the cubic crystal gamma-al2o3 at 400 degrees c, the tetragonal d-al2o3 appeared after 900 degrees c, it transformed to monoclinic theta-al2o3 at 1 060 degrees t, and it turned into rhombic hexahedron alpha-al2o3 at 1 200 degrees c.