Electro-optic crystal is one of the basic materials of all-solid-state laser, which can be used to modulate the laser propagation characteristic. Electro-optic modulation has a lot of advantages such as high efficiency, good stability, quick response and inertialessness etc. The development of novel highly efficient electro-optic crystal is of great significance for the development and application of all-solid-state laser technique. As a kind of multifunctional crystal material with excellent properties, potassium tantalate niobate crystal has remarkable electrooptic effect and photorefractive effect, which has been discovered and studied for more than a century. With the development of laser modulation technology and electro-optic crystal as the background, the research progress of potassium tantalate niobate crystal as a practical quadratic electro-optic crystal material is reviewed systematically in this paper.