The present disclosure describes a method of optimizing a design for manufacture (DFM) simulation. The method includes receiving an integrated circuit (IC) design data having a feature, receiving a process data having a parameter or a plurality of parameters, performing the DFM simulation, and optimizing the DFM simulation. The performing the DFM simulation includes generating a simulation output data using the IC design data and the process data. The optimizing the DFM simulation includes generating a performance index of the parameter or the plurality of parameters by the DFM simulation. The optimizing the DFM simulation includes adjusting the parameter or the plurality of parameters at outer loop, middle loop, and the inner loop. The optimizing the DFM simulation also includes locating a nadir of the performance index of the parameter or the plurality of parameters over a range of the parameter or the plurality of parameters.