Ferroelectric potassium lithium niobate crystals have been grown by using czochralski technique. The molecular formula of the crystal has been determined based on the Philips PW2400 X ray fluorescent spectra. Homogeneous and crack free samples about 6×6×7(a×b×c) were used to study the lattice vibration spectra using Raman and Infrared reflectivity spectroscopy. Compare with the lattice vibration spectra of other tungsten bronze (TB) type crystals, the symmetric bend vibration mode v 5 was split into three Raman lines, and the antisymmetric stretch vibration mode v 3 and antisymmetric bend vibration mode v 4 were all broadened greatly. This shows that Li ions in the C sites in the potassium lithium niobate crystal do influence on the Raman and inferred reflectivity spectra of [NbO 6] 7- octahedron greatly.