The simulation of casting process for bearing support structure and the material defect like porosity, distribution of porosity and volumetric porosity of the bearing structure is presented in this paper. The casting process has been iteratively simulated based on the pre designed casting parameters to forecast the real value of the porosity fractions. The finite element model of bearing support structure has also been simulated with GTN material model in order to compute the damage parameter over accumulated plastic strain with the predicted casting defects. The actual pore distributions on the bearing support structure are estimated from the real casting. The casting parameters are also be planned by iterative of casting simulations in order not to exceed the allowable casting defects. The simulated casting defects and casting parameters are also validated with real casting process. The simulated porosity fraction and actually obtained casting defects are well matched for the similar casting parameters.