Abstract: The borehole strain observation system at Jijitai was damaged and unable to resume normal operation due to a power supply failure, leading to its reinstallation and modification. To evaluate the reliability of the modified system, this paper assesses the data quality of the multi-component borehole strain observations after the modification by examining the accuracy of tidal factors, the self-consistency test of plane strain, relative in-situ calibration, and analysis of major interference factors. The results indicate that during the initial phase of instrument installation, the observation system was unstable and maintenance was not performed in a timely manner, resulting in overall poor data quality. After the observation system stabilized and with proper zero-point adjustment, the data quality improved significantly. The tidal factor accuracy met the standards for Class I deformation stations, the plane strain self-consistency test performed well, and the relative in-situ calibration coefficients of each component were close to the ideal value of 1. This suggests that the coupling between the strain probe, expansive cement, and bedrock was satisfactory, and the modified observation data quality was higher. Groundwater level changes remained the primary interference factor, with sharp fluctuations easily causing data inconsistencies. After removing groundwater interference through linear regression, the observation data quality further improved. It is essential to enhance the operational maintenance of the observation system to ensure stable data quality.