Aiming at the application requirements of digital and small-volume magnetic field sensors，it is necessary to explore a new magnetic field sensor，because existing inductive magnetic field sensors generally have the problems of complex hardware circuits，the need to use analog-to-digital conversion devices for digitalization， and it is difficult to achieve miniaturization. In this paper，a magnetic field sensor based on self-oscillating magnetic induction technology is proposed. Its measurement principle is based on the linear relationship between the duty cycle of the excitation voltage and the measured magnetic field. Compared with other magnetic field sensors，the output of the magnetic field sensor proposed in this paper is in the form of duty cycle，which does not require additional filtering circuits and analog-to-digital conversion circuits，and the hardware circuit is relatively simple， so it is beneficial to digitalization and miniaturization. Besides，the generation process of self-excited oscillation is analyzed，and the theoretical equation of excitation voltage duty cycle and measured magnetic field is established. A prototype is made to verify the feasibility of the magnetic field sensor based on self-excited oscillation magnetic induction technology. The results show that under open-loop conditions，the linearity of the sensor is 0.98% with the range of ±100 000 nT.
