The dissolution behavior of hydroxyapatite (HA) in a hydrothermal solution was investigated using a Morey-type autoclave over a range of 150-350℃ and a pH value range of 5-9. The results showed that the dissolubility of HA powder was determined as a function of temperature and time under constant pressure, and the temperature coefficient for the solubility of HA powder was positive. The rate of dissoluion of HA in the hydrothermal aqueous solution was mainly controlled by a polynuclear mechanism. The dissolution behavior of HA was affected mainly by the hydrothermal temperature and the dissolving activation energy. The effect of temperature was obviously more than that of the pH value of the solution. All rights reserved.