The construction of a smart grid cannot be separated from advanced sensing and measurement technologies. Compared with the traditional giant magneto-resistive current sensor with an opening in the magnetic concentrating ring, this paper proposes a sealed magnetic concentrating ring applied to the giant magneto-resistive current sensor, including the shape and structure of the sealed magnetic concentrating ring, and the air gap opening. The design of the size and the degree of unevenness, and the selection of the materials used in the sealed magnetic concentrator. Using COMSOL Multiphysics to simulate the model of the sealed magnetic concentrator, the relationship between the magnetic saturation degree of the sealed magnetic concentrator and the traditional magnetic concentrator and the uniformity of the magnetic field at the center of the air gap was compared and analyzed. The simulation results show that the magnetic concentrating ability of the sealed magnetic concentrator is 764 times that of the traditional open magnetic concentrator, and its structure can make the giant magneto-resistive sensor have lower hysteresis and better sensitivity than the traditional open magnetic ring. It can be used for real-time, accurate and reliable current measurement in the field; small current experiments have verified that the magnetic concentrating effect of the sealed magnetic concentrating ring is remarkable under weak magnetic fields. The magnetic field generated by the current of 0. 2 A and below acts on the giant magnetoresistive chip after being concentrated by the sealed magnetic concentrating ring. The output voltage of the giant magnetoresistive chip after sealing is more than 5 times that before sealing.