In an exemplary optical touch circuit and a LCD device using the same, an optical sensing unit is turned on or off according to an irradiation light intensity and accordingly generates a first signal. A first signal readout unit is electrically coupled to the optical sensing unit and turned on or off according to a first operation timing sequence and accordingly outputs the first signal. A touch reference unit is for providing a reference voltage. A second signal readout unit is turned on or off according to a second operation timing sequence and accordingly outputs the reference voltage. The touch sensing unit is electrically coupled to the first and second signal readout units and uses a voltage difference between the first signal and the reference voltage as a basis to determine that whether the optical touch circuit is touched or not.