The continuation of the observed gravity anomaly on an undulate terrain to the mean horizontal plane is carried out.Then the gravity field on this plane is separated by cutting the method into several fields caused by strata at different depths.Gravity fields resulting from different strata are downward continued to the corresponding depths,and the density of the strata is inversed.The density obtained by this method is the approximate density contribution of the strata,and is called apparent density imagery.In downward continuation of the gravity field,a new continuation method,i.e.,iteration approach,is used.The process of continuation is stable and has a relatively great depth of continuation.This continuation technology does not need to solve linear algebraic equation system and can overcome the computation time bottleneck which hinders the application of 3D inversion to practice.For a data set of 71×81 points,it takes 10s for 3D inversion on a 1.73 GHz PC.A real case in a certain area of Xinjiang is presented to demonstrate the effect of applying this method to inversion.