With the constantly development of High-Voltage Direct Current (HVDC) transmission system construction, the on-site calibration of DC current transformer has become the major research interest in HVDC transmission field. According to the research gap of the on-site transient performance calibration technology, the working principle of the existing DC current transformer and the on-site calibration method are analyzed. A set of portable transient performance calibration system for DC current transformer is devised based on signal resampling and pre-distorting adjustment. By revision, the system produces the large step current close to the simulation signal, and its 500 kHz high speed sending and collecting modules ensure the accuracy of the sampling and waveform restoring during the transient process. Furthermore, the first on-site transient performance test of the pole and converter valve DC current transformers has been carried out with the system in Sunan UPFC Project. The rising time, maximum overshoot and the transient delay of the pole and converter valve transformers are tested, and the results provide the basis for the evaluation of the DC current transformers. The technology has a good application prospect for the on-site DC current transformer calibration. This work is supported by National Natural Science Foundation of China (No. 51707090) and Science and Technology Project of State Grid Corporation of China “Key Technical Research and Application of On-site Test and Operation Maintenance for UHVDC Control and Protection System”.