The orthogonal fundamental mode fluxgate has the advantages of wide frequency band, low noise and small volume compared with the traditional parallel excitation second harmonic fluxgate. In order to meet the application requirements in geomagnetic navigation, electromagnetic tracking and other fields, and further increase the response bandwidth, a digital quadrature fundamental mode fluxgate sensor simulation model was established, and a hardware circuit composed of high-speed ADC, FPGA and high-precision DAC was built. The related FPGA program was developed, the correctness and feasibility of the digital demodulation scheme were verified. After testing, the digital quadrature fundamental mode fluxgate sensor has a bandwidth of 15 kHz, which has obvious advantages, and shows a good prospect in the intelligentization of orthogonal compensation and gain calibration.