Abstract: KTa1-xNbxO3(KTN) crystal exhibits an extremely large quadratic electro-optic effect, which can manipulate the phase, intensity and propagation direction of the light. KTN devices can be applied not only to optical communications, but also to various other fields that use optical beams, such as displays, medical use. The influence of Ta/Nb fraction, crystal temperature, inclusions and composition variation on the Kerr effect of KTN crystals is discussed in this paper. Several KTN devices based on the Kerr effect, including electro-optic modulator, optical switch, beam scanner, varifocal lens and spectrometer are introduced. The basic principle, research progress and application prospect of the devices are described. The trends in the research and development of the KTN devices is reviewed and predicted.