This paper designs an experimental device for measuring weak magnetic fields through simple harmonic motion. By adjusting the current I in the Helmholtz coil, the magnetic field intensity B at the magnetic columns position is precisely controlled. Using a high-speed camera and Tracker software, the vibration period Tof the magnetic column under different magnetic fields is recorded. Then, Origin software is used to fit the relationship between the square of angular frequency w2and current I. Combined with the theoretical model, this allows the calculation of the size and direction of the weak magnetic field.