Abstract: The self-controllable DC control and protection device is a critical equipment in HVDC transmission projects, and the performance of its AC sampling plug-in directly determines the measurement accuracy and control reliability of the device. Relying on the localization substitution project of the MACH2 platform in the Debao HVDC project, this paper designs an automatic calibration test system for intelligent AC sampling plug-ins in self-controllable DC control and protection devices. The system enables automatic calculation of calibration coefficients and phase angle errors and stores them in the MCU chip, significantly improving the measurement accuracy of AC sampling plug-ins and production test efficiency. Meanwhile, the system supports real-time uploading of calibration coefficients, phase angle errors, and test results to the cloud platform, providing data support for big data analysis and quality traceability, demonstrating promising engineering application prospects.