In the roasting process stageeach component of the cell of aluminum performs unsteadily. Monitoring the currents of both anodes and cathodes of the cell at regular intervals is quite necessary. Rogowski coil is used to measure heavy direct currents (DC) of both anodes and cathodes of the cell. The paper introduces the principle of the current distribution characteristic of the cell and, introduces the principle of Rogowski coil used to measure DC and, analyzes the performances of the Rogowski coil. Some important considerations on improving the performance of Rogowski coil in DC measurement applications have been presented. The output variation with temperature and method of calibration of the instrumentation are presented as well. The experiment results are provided to confirm the validity of the proposed method for inspecting the state of the cell during the electrolytic roasting process.