B-dot sensors are widely used in electromagnetic pulse (EMP) measurements due to their wide frequency band, small size, and good stability. There is a difference between any theoretical model and the actual situation, thus the B-dot sensor must be calibrated under the laboratory environment. Aiming at the shortcomings of traditional time-domain calibration methods, this paper proposes a frequency-domain calibration method based on OE model. The method uses the OE model transfer function of single input and single output to characterize the frequency response characteristics of the B-dot sensor, and then obtains the sensitivity coefficient of the frequency range in which the sensor actually works by partial linear regression. According to verification experiment, it can be determined that this method can effectively avoid the influence on calibration accuracy of overshoot or ringing caused by impedance mutation.