Solving 3D structural gravimetric problems, it is many times very helpful to aproximate studied geological environment by set of inhomogeneous, rectangular, arbitrarily truncated prisms. To meet modelling requirements, it is necessary to obtain solutions for wide spectrum of density changes within the prism. Software package GEOPHYS0 created by Starostenko and Legostaeva (1998) is based on calculation of gravity field caused by inhomogeneous, rectangular, arbitrarily truncated prism. It is a software package that enables to calculate 3D gravity effect caused by anomalous density layer with arbitrary upper and lower boundary. Density of a layer can be constant or can change linearly or exponencialy with depth. Prior to the calculation of 3D gravity effect, it is necessary to construct isolines maps of Bouguer anomalies and depths that are consequently transformed to the vector form.