We present an object-oriented simulator for 3D digital breast tomosynthesis (DBT) system using C++ programming language. The simulator is capable of implementing different iterative reconstruction and total variation (TV) regularization methods on the real world phantom models. A user friendly graphical user interface (GUI) helps users to select and run the desired methods on the designed phantom models. Results from a phantom study that mimics a real tomosynthesis problem, including the images of the layer of the interest (LOI) and structural similarity (SSIM) diagrams are presented.