Abstract: In the field of industrial automation, the accuracy and reliability of level measurement technology are crucial for process control and quality assurance. In light of the limitations of existing calibration methods in long-distance and high-precision measurements, this study has developed a new type of high-precision calibration system based on the 80-meter high-precision large-length laser interferometer of the National Institute of Metrology of China. The system provides standard values with an uncertainty of U=\mathrmQ\left0.15\mathrm\mu \mathrmm, 2\times 10^-7L\right （k=2）outside the triangular area formed by the three light beams. The calibration measurement range is (0～70) m, and the expanded uncertainty of the reflective level gauge with a graduation value of 0.1mm is 0.3mm. The system has a wide applicability and can meet the calibration requirements of buoyancy level gauges and high-precision magnetostrictive displacement sensors by designing relevant tooling. The measurement range covers (0～80) m, and the measurement efficiency is high, with the measurement time for each calibration point not exceeding 15 seconds. The study also quantitatively analyzed the impact of the inclination angle on the measurement results, and the experimental results show that an inclination of 1° can have an impact of up to 3mm on the measurement results. This new calibration system significantly improves the calibration accuracy of level gauges and has a broad prospect for industrial applications.