The 4D model is used to invert dynamic variation for crustal density and vertical deformation from the data of gravity measurement and leveling survey.The inverse formulae are derived.Using the formulae, data of gravity measurement and leveling survey in the Hexi region of Gansu province and northwestern Yunnan province are computed, for study on variations of the lower crustal interface density and vertical deformation of Moho surface with time.Relationship between the variations and moderate-strong earthquakes in the two regions is analysed.The results show that density of lower crustal interface reduced on a large scale and upheaval of a wide range of Moho surface in the two regions may be a geophysical criterion in crustal depth for earthquake prediction in one year.Strong earthquakes often occur in regions that are located between upheaval and subsidence of the Moho surface or density reduction and density increase of the interface.