Magnetic flux sensors utilize the magnetoelastic effect of ferromagnetic materials to establish the relationship between changes in magnetic conductivity and stress and temperature. By measuring changes in magnetic permeability, the tension of ferromagnetic material components is measured. This measurement method is non-destructive and non-contact, suitable for measuring the internal forces of stay cables, suspension rods, tie rods, external cables, and prestressed tendons. It can be used for construction monitoring of prestressed tendons and long-term safety monitoring. The article provides a detailed description of the principle, performance, and engineering applications of magnetic flux sensors