Absorption band countered on wave numbers 3504 and 6843cm−1have been observed in potassium niobate crystals. These absorption bands correspond to the transition energies of O–H stretching vibration, from the ground state to the first excited state and to the second excited state, respectively. Absorption bands around 3992 and 4476cm−1are attributed to the combination of O–H vibration plus libration. The integrated absorption intensities around 3504, 3992, and 4476cm−1are three dimensional polarization dependent which indicates the motion properties of hydrogen ions in the lattice. ©1997 American Institute of Physics.