This study presents a novel magnetic field shielding structure designed specifically for Tunnel Magnetoresistance (TMR) sensor arrays used in large current AC scenarios. The application of current sensors is often challenged by the interference from adjacent phases, particularly the magnetic field interference from low-frequency large currents. This study begins by analyzing the principle of current measurement using TMR devices and arrays, then elucidates the principle of low-frequency magnetic field shielding through flux diversion and eddy damping mechanisms, and introduces a new algorithm for evaluating shielding effectiveness. A segmented magnetic shield with novel protruded structure is designed for three-phase parallel large current. Finite element methods (FEM) results demonstrate that the proposed shielding structure can significantly reduce the interference from adjacent magnetic fields, reducing the error from 0.985% to 0.76%. Furthermore, the 3-D FEM confirms the effectiveness and manufacturability of the shielding structure. This research provides an effective magnetic field shielding solution for the measurement of AC large currents, which is of significant importance for improving the accuracy of current measurement.