The potassium niobate (KNbO3) is prepared with niobium oxide (Nb2O5) and potassium hydroxide (KOH) as source material by hydrothermal method, which adds different kinds of potassium salt, for example, KCL, K2SO4, K2CO3, KBr. The influence of different potassiums on crystal texture, microstructure, output and fluorescence of the complex KNbO3 is studied by X-ray diffraction (XRD), Raman spectrum, scanning electron microscope (SEM), infrared spectroscopy (FTIR) and fluorescence spectra (PL). Results show that the productivity is improved greatly by the adding of potassium salt. The kind of potassium salt is a critical factor for the structure and morphological profile of the KNbO3. When the added potassium salt is KCl or KBr, the well crystallized KNbO3 rods whose structures are rhombohedral and ortho rhombic form respectively are formed with the width of 0.5～1 μm and the length of 1～10 μm. Using K2CO3 or K2SO4 as the added potassium salt, the formed KNbO3 crystals whose structure are rhombohedral and ortho rhombic form respectively are irregular granular structures instead of rod-like structures. FTIR results indicate that the crystal show Nb＝O and Nb－O－Nb vibration peaks at 1383, 1087, 1050, 879, 614 cm-1. The fluorescence emissions of the KNbO3 samples are detected to appear the characteristic peaks at the wavelengths of 396, 450, 467,481, 491 nm.