Sodium niobate NaNbO3 hydrate (NN-hydrate) particles with a plate-like morphology were prepared at 140 degrees C for 2h in 12mol/L of NaOH by the hydrothermal method. Bar-like Na(8)Nb(6)O(19)13H(2)O particles were synthesized at as low as 100 degrees C for 2h. This work demonstrates that by carefully optimizing the reaction condition, we can selectively fabricate niobate structures, including the bar-like, plate-like, fibers and cube particles through a direct reaction between NaOH solution and Nb2O5. It was found that Nb6O198- formed was an important premise for formation of the NN-hydrate, and lower [OH-] was not favorable in preparing the NN-hydrate as there was an optimum [OH-]. Through researching effects of the reaction temperature, time, concentration of NaOH, and content of Nb2O5 on the NN-hydrate structure and evolution, the formation mechanism from solid reactants to the intermediate were investigated. After calcining at 800 degrees C, the synthesized NN-hydrate particles made a phase almost transform to the perovskite NaNbO3, and the morphology of these calcined particles was still plate-like.