Zn ions doped hydroxyapatite can not only give rise to the change in the crystal structure and microstructure of whiskers, but also affect their thermal stability and other biological properties. In this paper, zinc doped HA (Zn-HA) whiskers were successfully prepared by hydrothermal method, and their crystal structure, forming process, thermal stability and the crystalline morphology were studied by XRD, FTIR and SEM. It is shown that Zn-HA whiskers with single phase could be obtained when the Zn2+ doping content is less than 5%; when the Zn2+doping content is 5%, a small amount of impurity phase CaZn2(PO4)2·2H2O begin to appear in the products; when doping content is 8%, a significant Zn(PO3)2 impurity peaks appear. As hydrothermal temperature increases, the OH- in the solution releases continuously, and accompanying the formation and growth of HA crystal nucleus, there are little CaZn2(PO4)2·2H2O and Ca3(PO4)2 impurity phase, and Zn-HA is formed by dissolution and precipitation. When the doping amount of Zn2+ is within 0-8%, the crystallinity of the products gradually decreases with the Zn2+ doping amount increases, giving a slight increase in the cell parameters a and c basically unchanged. Zn2+ doped HA whiskers are heat treated in >800 ℃ environment. The increase of Zn2+ doping and the change of heat treatment temperature can promote the transformation of HA whisker to β-TCP forming biphasic calcium phosphate.