Based on the current settlement monitoring requirements of high energy photon source (HEPS), the research group designs the key parameters and structure, and develops the first micron monopolar plate capacitive hydrostatic level sensor prototype in China. This article focuses on the calibration and accuracy verification of the level sensor. To address the problems of low calibration accuracy and high machining requirements of the traditional standard block and translation stages calibration method, the single level sensor direct calibration method and multi-segment fitting parameter acquisition scheme are innovatively adopted to realize the micron calibration within 10 mm range. Meanwhile, the laser feedback interferometer combines with nano translation stages is proposed to directly monitor the change of liquid level to realize the full range accuracy verification of single level sensor. And the accuracy is 3 μm. The accuracy of the two-point monitoring system with 7 m distance is evaluated by the heavy-duty translation stages. The relative monitoring accuracy of height can reach 5 μm in the range of 10mm. Results show that the accuracy of the prototype meets the design requirements, which can provide a reliable means for high-precision height monitoring of large-scale devices in China.