The present invention discloses a tunable optical integrated element using liquid crystal as an active layer, which is applied to filters, couplers or optical add/drop multiplexer. The present invention includes a layer of liquid crystal as an active layer, a first waveguide with grating and a second waveguide, an isolation layer, a pair of electrodes. By applying the external voltage to control the direction of the liquid crystal, the refractive index of the waveguide changes in accordance with the modulation of the electric field. Thus invention has the features of simple structure, easy assembling, lower cost and integrating ability.