In this study, sedimentary basins were modeled by using the variable density contrast. In a sedimentary basin which might be modeled by a series of prisms juxtaposed with each other, density variation with depth was represented by quadratic function. The initial depths of the prisms were obtained by using the gravity anomaly of an infinite horizontal slab for the modeling. These depths were improved by taking into account the differences between the observed and calculated anomalies. The method was successfully examined on the theoretical models and then applied to Erzincan-Cayirli field data.