High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure conditions. Effects of the titanium source and reaction conditions on the hydrothermal reaction rate, product phase component, and morphology of whiskers were investigated. The results show that the reactivity of hydrated titania, anatase TiO 2 , and rutile TiO 2 with KOH decreases in turn, and with hydrated titania as titanium source, it is difficult to obtain potassium hexatitanate whiskers with good morphology. In contrast, uniform potassium hexatitanate whiskers with a length of 10-20 μm and a diameter of 200-700 nm were obtained using anatase TiO 2 as titanium source. The investigation demonstrates that the initial KOH concentration, annealing temperature and time, molar ratio of K 2 O/TiO 2 , etc. significantly affect the morphology of the as-synthesized whiskers. The optimized synthesis condition is as follows: anatase as a titanium source; 10 wt.% KOH solution; annealing temperature and time of 300°C and 5 h, respectively; K 2 O/TiO 2 molar ratio of 5, etc. A rhombic potassium hexatitanate was prepared under the optimum condition and the whisker grew along the [110] direction. The reaction mechanism was discussed.