Nano-scale hydroxyl magnesium silicate was synthesized successfully by using hydrothermal method. The composition of as-prepared powder was proved chrysotile which adheres to monoclinic crystal system (a kind of hydroxyl magnesium silicate) by using X-ray Diffraction (XRD) technology. The morphology and microstructure of chrysotile powder were characterized by using scanning electron microscope (SEM) and transmission electron microscope (TEM). Nano-particles and nano-rods were observed in SEM micrograph. Moreover, smaller-size nano-particles and nano-fibres were observed by using TEM. Based on results of SEM and TEM, the growth mechanism of chrysotile powder under hydrothermal conditions was discussed.