Abstract: A light-tunable device based on dye-doped nematic liquid crystal is fabricated, and its switching characteristics are investigated. The cell is made by parallel arrangement of two glass with indium tin oxide (ITO) layer. Smart glass is made by filling the mixture of dye and nematic liquid crystal into cell. After applying an electric field, electric responsive nematic liquid crystal will align parallel to electric field. The rotation of liquid crystal molecule will give rise to the movement of the dye molecule. Meanwhile, distrubution of liquid crystal molecule will change from multidomain to monodomain, which induces smart glass state changing from scattering to transparency and achieving the function of dark-brightness switch. By varying the concentration of dye, driven voltage, the smart glass exhibits different performance. Threshold voltage of device rises while cell thickness goes up. Optimized performance will be obtained with the condition of 5% dye concentration, 30 m cell thickness, when threshold voltage is 5V, saturation voltage is 15 V.