High purity(99.99%) spherical particles of hydrated Basic Aluminum Salts(BAS) were prepared by a homogeneous precipitation process utilizing the urea decomposition reaction and characterized by XRD, SEM, TG-DTA, IR and PSA methods. Amorphous hydrated BAS was precipitated in the range of pH 4~6. The molar ratio [Al3+]/[SO42-] for the precipitate particles was about 3.7. With increasing the concentration of aluminum sulfate the precipitation of the hydrated BAS occurred slowly and the precipitate particles with a narrow size distribution were fine(1-2${mu}{ extrm}{m}$ in diameter). At temperatures in the range 400$^{circ}$to 95$0^{circ}C$, desulfurization and dehydroxylization resulted in weight loss with 22%. When the precipitate particles were thermally treated, the crystlline ${gamma}$-Al2O3 was identifited by XRD at 50$0^{circ}C$ and ${gamma}$-Al2O3 particles were transformed into $alpha$-Al2O3 at 100$0^{circ}C$. A vermicular network was produced by calcining at 125$0^{circ}C$ for 30min.