Semiconductor photocatalysis for harvasting and utilizaing solar energy to solve worldwide environmental pollution and energy shortage is attracted flourishing interest. A complete understanding of structure-function relationships in well-defined model catalysts is essential to better understanding "real world" photocatalysis as well as rationally design photocatalysts. Well-defined NaNbO3 crystals are successful synthesized via facile hydrothermal method. Systematically characterzation is performed by XRD, Raman, SEM, BET specific surface area analyzer and DRUV-Vis. The results of XRD and Raman show that the as-prepared samples are pure orthorhombic NaNbO3 and NaNbO3 with different morphology possess various mainly exposed facets. On the basis of statistical SEM measurements, it presents that the shape evolution of NaNbO3 is shown to be dependent on the reaction time, from nanowires to a mixture of nanowires and microcubes, and finally to microcubes, and realized the morphology control systhesis of NaNbO3. The possible growth mechanism is proposed combined with previous study, highlighting the crucial role of P123. The photocatalytic performance of the as-prepared NaNbO3 crystals is assessed towards aqueous methyl bule under UV illumination, and compared with that of commercial NaNbO3 powders. DRUV-Vis evidenced that the absorption edge of NaNbO3 nanowires is blue shifted due to quantum size effect. The results show that the photoreactivity is morphology-dependent, with the BET specific surface area normalized reaction rate constants follow the order NaNbO3 nanowires>NaNbO3 microcubes >commercial NaNbO3. The exposed facets play a crucial role in determining the observed photocatalytic activity.