Abstract: The transfer function of the measurement system is established on the lumped parameter model of Rogowski coil, and the optimal damping resistor of the differential type of Rogowski coil is obtained under the steady sine input. In this paper, the amplitude-frequency characteristics of RC integrator circuit and active integrator circuit are compared, and also the actual bandwidths of the two measurement systems are determined by the measurement precision. Using active integrator circuit, the measuring bandwidth is extended and the transient performance is improved. Theoretical analysis indicates that the optimal structure and parameters can inhibit the integrator drift. Therefore, the measuring system has the features of high accuracy and reliability. The experimental results in SG-Ⅲ have p