Design of optimization of thin film solar cell module based on Cu(In,Ga)Se(2) (CIGS) is investigated through a simulation model. At first, a numerical model which is equivalent to a practical cell module and represents one diode electrical circuit method is sought in FEA (Finite Element Analysis) and several parameters are adjusted. In FEA, the distribution of electric potential within each layer is shown with accordance to the given inputs. Next, to find the optimal design, four design variables (factors) which have three levels each are chosen and Design of Experimental (DOE) is performed so that the order of influences to performance is arranged. In DOE, a series of simulation follows the prepared orthogonal array, which is a sort of combinations by factors and levels, then analysis of variance (ANOVA) table is built up to screen unimportant design variables. Finally, the surface response function, which represents the relationship between important design variables and the purposed performance such as efficiency and fill factor (FF), is found and shown into equipotential graphs.