Abstract: A cholesteric liquid crystal writing board, which can display a writing track, includes a cholesteric liquid crystal device, an optical layer, a photo-sensing array and a voltage control circuit. The cholesteric liquid crystal device includes plural liquid crystal control areas. The optical layer has plural optical openings. The photo-sensing array includes plural photo sensors arranged in an array. The photo sensors are disposed corresponding to the optical openings. One of the photo sensors senses a luminous flux change and generates an erasing signal accordingly. The voltage control circuit receives the erasing signal and outputs a voltage signal accordingly to the liquid crystal control areas corresponding to the photo sensors having the luminous flux change, such that a part or all of cholesteric liquid crystals corresponding to the liquid crystal control areas are morphologically changed so as to clear a part or all of the writing trace.