Hydroxyapatite (HAp) nanoparticles with uniform morphologies and controllable size have been synthesized successfully by low-temperature hydrothermal method. The cationic surfactant CTAB as a template is used to regulate the nucleation and crystal growth. The synthesized powders were characterized using X-ray diffraction, Fourier transform infrared spectrograph and transmission electron microscopy. The results indicate that the obtained particles are uniform rod-like monocrystals. Compared with the reaction time, the temperature of reaction is more significant variable in altering the HAp morphology and size. Furthermore, the behavior mechanism of CTAB is discussed.