DC transformer is the core equipment to provide control, protection and measurement signal in DC transmission project, its reliable work directly affects the safety and stability of the system. In order to develop a calibrator for DC transformer of Zhangbei VSC-HVDC Project, this paper studies a precise synchronous verification scheme and a high-speed FT3 message reception and analysis scheme through the analysis of non synchronous verification and secondary signal processing, which meets the needs of FT3 message analysis under different sampling rates during field verification of transformer, and is suitable for Zhangbei VSC-HVDC Project equipment In this paper, the hardware and software structure of the calibrator system are also studied, and the error calibration test of the calibrator is carried out. Finally, the calibrator is applied in a converter station of Zhangbei VSC-HVDC Project.