The basic principle of the fluxgate sensor is based on the nonlinear magnetization characteristics of the core material. The sensitive component is a core made of high magnetic permeability and easy-saturated material. There are two windings around the core: one is an excitation coil. The other is the signal coil. Under the magnetization of the alternating excitation signal fl, the magnetic permeability of the iron core undergoes periodic saturation and non-saturation changes, so that the induction coil surrounding the iron core induces a signal reflecting the external magnetic field, the signal including fl, 2f1 and other harmonic components, where the even harmonics contain information about the external magnetic field, which can be extracted by a specific detection circuit.