Abstract: The Qiangguang-Ⅰ (QG-Ⅰ) accelerator can produce high current pulses with rise time of about 100 ns and amplitude of about 2 MA. The load current is usually monitored by self-integrating Rogowski coils. In order to verify the obtained results of the coils, a differential loop with fast response time, relatively simple design, and appropriate performance against electromagnetic noise, has been developed. Calibration experiments show that the differential loop has a response time of about 1.2 ns, a response frequency range from 10 kHz to 100 MHz, and a sensitivity of 6.1310-11(Vs)/A. The fast response may help to monitor transient variation of the load current related to some rapid physical processes. The differential loop has been tested within short-circuit diode of QG-I accelerator and compared with self-integrating Rogowski coils. The current waveforms obtained through numerical integration of the loop signal exhibit good agreements with those from the coils, with an amplitude deviation less than 10%. Comparison of the results confirms the availability of the loop, and also verifies the reliability of the load current measurements on the accelerator.