Abstract: As one of the lead-free piezoelectric systems, potassium sodium niobate (K, Na)NbO₃, abbreviated as KNN has been a research interest due to its high piezoelectric property, high Curie temperature as well as the tailored phase structures. However, there are still some problems in the study of one dimensional (1D) KNN structures. For instance, the orientation growth of crystals is difficult to be controlled, the piezoelectric properties of the product should be further enhanced. In this paper, the hydrothermal synthesis method was applied to fabricate the 1D KNN structures on the Nb-doped SrTiO₃ (NSTO) substrate. The hydrothermal temperature, Nb₂O₅ concentration and the hydrothermal time were studied, respectively, and the oriented KNN nanorod arrays (NRAs) with high quality were achieved. The results show that the KNN NRAs with single orientation, good crystallinity and high piezoelectric response can be obtained when the hydrothermal temperature is 190 ℃, the Nb₂O₅ concentration is 40 mL/g, and the reaction time is 18 h, respectively.