A liquid crystal grating panel, a stereo display device and a display method thereof are disclosed. The liquid crystal grating panel comprises an upper polarizer, an upper substrate, a lower substrate, a first electrode, a second electrode, a third electrode and liquid crystals; the third electrode is separated from the first electrode through an insulating layer; the liquid crystals are disposed between the upper substrate and the lower substrate; the first electrode is used for generating an electric field with the second electrode at first frame scanning periods of image scanning to form a first grating; and the third electrode is used for generating an electric field with the second electrode at second frame scanning periods of image scanning to form a second grating.