Abstract: In order to overcome the interference of complex electromagnetic signals on electromagnetic vibration energy harvester in power application scenarios, and to achieve frequency matching between the resonant frequency of device and the environmental vibration frequency, a frequency tuning method in which soft magnetic materials are employed to modulate the magnetic field is proposed. By establishing the dynamic model and magnetic field coupling model of the electromagnetic energy harvester, the influence of magnetic nonlinearity and geometric nonlinearity on the resonant frequency is clarified. The influence mechanism of permanent magnet and soft magnetic material on the internal magnetic field distribution of the energy harvester is studied, followed by the completion of frequency tuning unit and overall structural design. A prototype was fabricated and performance validation tests were conducted to verify the effectiveness. The research results show that the frequency tuning method based on soft magnetic material realizes a frequency range of 96~139 Hz, achieving a relative tuning range of 44.8%. Compared with conventional frequency tuning methods of utilizing permanent magnet, the proposed method not only realizes wide-range and high-precision resonance frequency adjustment in electromagnetic vibration energy harvester, but also demonstrates dual-functional advantages of mitigating external magnetic interference while suppressing internal magnetic flux leakage. This dual capability significantly enhances the operational reliability of the energy harvester under harsh magnetic field conditions.