Abstract: In order to meet the growing requirements of some national projects, such as the aerospace, monitoring of fuel liquid level, as a key parameter of the flight evaluation, directly affects the efficiency of all kinds of crafts. A liquid level sensor system, which can achieve both single-point discrete and multi-point continuous measurement, was designed based on the bending loss of the plastic optical fiber and the total internal reflection principle. After description of the theory, the actual equipment was used to test the theoretical analysis, illustrate the operating principle, systematical composition and the advantages of the technology were inustrated, simultaneously the feasibility of liquid level measuring experiments in theory was analyzed. Furthermore, both discrete and continuous liquid level sensing systems were finished. The verifying experimental system was also set up. The experimental results show the proposed liquid level sensor system not only can realize the measurement of the liquid level, but also has good consistency and simple implementation. The continuous liquid level sensing system can reach the test range of 450 mm with a sensitivity of 0.808 3 W/mm, showing a significant reference for the engineering application.