The presented paper is leaning on the experience of the 3D density modeling during the study of sedimentary basins and Earth's crust in the Arctic and Far-Eastern areas. The main stages of creation 3D density model such as analysis of geologic-geophysical data, tectonic subdivision of areas under investigation, methods of density model approximation and principals of modeling are stated. These methods take in consideration the whole reliable geologic-geophysical information and allow to use it for the combine interpretation.