Abstract: As a new generation of magnetic sensors, tunnel magnetoresistive sensors possess such advantages as good temperature characteristics, high sensitivity and so on, so it has been researched and widely applied in electric power measurement. External magnetic field interference is the key factor impacting the measurement accuracy of the magnetic sensor. In allusion to current measurement scenario of DC distribution network, firstly, an external magnetic field interference model of tunnel magnetoresistive element sensor array was established. Secondly, based on the algorithm of adaptive filtering analysis the optimal structural parameters of the magnetic sensor was proposed, and the effectiveness of the established model was verified by numerical analysis and Finite element simulation. Research results show that when the measured current is between ±50 A and ±300 A, and the ratio of the array radius to the busbar spacing is 1:2.5, the impact of external magnetic field is minimal. By means of adaptive filtering algorithm the measuring error of magnetic sensor can be reduced to less than 1%.