Abstract: A cooling device of liquid crystal projector is utilized to cool a liquid crystal panel and polarizer of an optical system in a liquid crystal projector; when the optical system of the present invention is heated by a light projection, coolant will carry the heat of the liquid crystal panel and polarizer of the optical system away, and a flow guiding device is used to lead the coolant to flow so as to cool the high temperature coolant by means of a heat dissipating device, then the heat is dissipated to outside environment thereby. After the temperature of the coolant is lowered, it is led to flow through the liquid crystal panel and polarizer again by means of the flow-guiding device, so as to repeat a cooling cycle.