An optical fiber sensor to accurately judge the level of a point is presented in this paper. Three fibers are used in the sensor, one as the source to emit infrared light, and the others as the differential inputs to absorb the scattering of light. Adopting a differential structure of dual signal fibers helps removing the interference of external environment and the change of the intensity of the light source. When the sensor contacts the liquid, the emitted light will be scatted by the liquid so that the output voltage will have significant difference from it when the sensor is above the liquid. A 45 degree oblique end-face of fibers is not just used to reduce the adhesion of liquid but also can increase discrepancy between differential inputs due to different scattered light intensity at different position, and then enhance the sensitivity. Base on this point, the optical fiber point liquid level sensor is designed and its working performance is investigated by experiments. The experimental results indicated stability, accuracy and excellent performance in the use of this sensor to measure the status of liquid level. And the safety will be ensured for the characteristic of fiber and excellent electrical isolation.