Considering the difficulty to precisely indicate the specified height for transparent or semitransparent thin liquid column, a novel fiber-optic liquid level sensor is reported which remarkably enhances the sensitivity by regulating the external light path based on the principle of light refraction. The structure and working principle of this sensor is introduced. A light path model is developed on the condition that the incident light ray obliquely penetrates the medium in the liquid level indicator. The formulae of deflection angle are deduced. Factors affecting the precision of the sensor are analyzed by means of an example. Finally the feasibility of this novel design is verified by experiments.