In order to better investigate the relationship between geomagnetic anomaly changes and earthquakes, the distribution characteristics of the change modulus of epicenter position of earthquakes with ML ≥ 4.0 within the measurement area were studied by using modular quantification calculation method based on the mobile geomagnetic vector data of Hebei and surrounding areas from 2017 to 2021. The results show that : ① The image distribution morphology of H-mode and F-mode is very similar. The main abnormal forms and geological structures in the survey area have a weak control over the changes in the lithospheric magnetic field. ②The temporal variation of the lithospheric magnetic field in the survey area is generally stable, with fluctuations in some areas 80% of the earthquake cases occur in the low value areas of the H-mode and F-mode, and the values of the ratio（the ratio of the epicenter modulus to the mean value of the modulus measurement area） are concentrated in the range of 0.2 to 0.9. There is no linear correlation between the earthquake magnitude and the ratio.③Using the standard mode as the reference threshold for local mode value anomalies, the reference anomaly thresholds for H mode and F mode were obtained to be 3.10 and 3.54, respectively. Using an improved R-value evaluation method, a R-value of 0.3 was obtained based on the "mean of the modulus measurement area". It is concluded that the level of earthquake prediction based on modulus anomalies is still very low, and the research and judgment of mobile geomagnetic anomalies is still in the exploratory stage.