Abstract: The stabilization of terbium(IV) with hexametaphosphate in aqueous solution has been studied in the paper. Astable solution of terbium( IV ) with red brown color was obtained, by dissolving the hydrated oxide of terbi-um(IV) in sodium hexametaphosphate solution. This solution has a broad band absorption near 375nm, which is considered to be, one of characteristics of terbium(IV) compounds. The color of the solution of terbium(IV) will remain unchanged for a long time at 6<pH<13. The red brown solution of terbium(IV) possesses some colloid properties, i. e. Tyndal effect, electrophoresis and flocculation by adding a small amount of electrolyte. It is confirmed by chemical analysis that the flocculation product is Tb(IV) hydrated oxide. Thus it can be seen that the stabilization of Tb(IV) in aqueous solution is due to the formation of colloid solution.