By analyzing the measuring principle of Rogowski coil, a new current transducer with the Rogowski coil is proposed for on-line measuring indoor power supply load currents. The Rogowski coil is designed with plastic ring and enamel-insulated copper wire, which are used as its framework and winding wire, respectively, and the signal processing circuit is designed with two precise operating amplifiers by employing OPA 211 with low noise. Amongst, the first amplifier serves to amplify the inducted millivolt signal form the Rogowski coil, while the second amplifier serves to restore the measured current signal and filter the yielded interrupt noise signal. The experiment results show that the proposed Rogowski coil and its signal processing circuit has merits of good linearity, high measuring precision and low manufacturing cost, which meets the measuring requirement of industry frequency current transducer with 0.5 grade and has important engineering application value.