We present a simple and efficient way to improve the performance of the twisted nematic liquid crystal (LC) system by doping a small amount of n-alcohols. The LCs modified by n-hexanol demonstrates the optimum electro-optical properties of lower driving voltage and shorter response time. Our measurements indicate that the n-alcohols can be treated as surfactants to modify LCs for lowering zenithal anchoring energy relative to undoped LCs. Without the drawbacks of precipitation and aggregation that the nanoparticles could have, the method of doping n-alcohol liquids provides a more stable and reliable choice to apply in the various LC display systems.