Abstarct: The final goal in geophysical methods is to interpret and determine the characteristics of geological structures from measured data. Typically, in modeling methods physical characterestic such as density or susceptibility and geometric properties such as structure depth as model parameters and geophysical measurements, they are considered as assumptions (data).Through being a lot of sedimentary structures in Iran such as oil traps which are economically important, study and modeling of baxsement topography might be deliver valuable information. Sedimentary basins have always been considered as one of the prerequisites for the presence of hydrocarbon resources, and the study of the geometry of these basins has always been of great importance. In this study, 3D non-linear inverse modeling of gravity and magnetic data is used to determine topography of baxsement. Two most useful models for modeling a three dimensional baxsement are juxtaposing rectangular prisms and the polygon. With the model of juxtaposing rectangular prisms, inversion become not only faster, also will be avoid of the difficulties associated with the model of Talwani and Ewing. In this study, a three-dimensional baxsement is modeled by equating it to a series of juxtaposing rectangular prisms and calculating their thicknesses. In order to demonstrate the efficiency of the method, understanding how the method works and its details, the modeling of free noise and noisy gravity and magnetic data was first performed. At the end of the modeling of real gravity data from the Cheshire England and real magnetic data from the North-West Iran (Aslanduz). All the programs used in this article are provided by the author in the MATLAB software environment.