Abstract: In this paper, we use a Bayesian principle-based gravity leveling method to uniformly process 16 periods of land-based mobile gravity observations from 2009-2017 in North China, and study the dynamic characteristics of the regional gravity field in conjunction with four earthquakes （M≥4.5） that have struck the studied area since 2009. Further, we study the characteristics of the isostatic gravity anomaly in North China, and analyze the relationship between regional gravity field changes and deep density structure based on the Bouguer gravity anomaly, sedimentary sequences gravity anomaly and Moho gravity anomaly in the studied area to characterize the three-dimensional density structure in North China. The results show that, the four earthquakes （M≥4.5） in the studied area in recent years have been located near the contours of the regional differential gravity field and the zero-value of the cumulative gravity field, the abnormally shifting gradient zones and the bends of the gradient zones, the unbalanced zones in the deep structure where the theoretical equilibrium thickness differs from theactual crustal thickness, and the high and low densities of the three-dimensional density structure inside the transition zone.