Design is often multidisciplinary involving several design elements with various types of objectives and constraints. It's very difficult to make a complex design with own paper and pen because some easily described with mathematical formula, other better modeled as descriptive complex design. This paper describes a method base Design Structure Matrix (DSM) with a common approach to be used for optimization design arrangement. This paper presents a new approach for engine room design based on the modularization concept inconsideration of series ships. The characteristics of the proposed method are as follows: Attention was paid to piping systems of series ships with different sizes. The cost and weight of the piping system as well as the similarity and the commonness of the modules and arrangements were considered. To define an effective module that could be commonly used in different ships, a design structure matrix was adopted. Modularization is divided into two important points: common modularization and optional modularization. A genetic algorithm is used to compose the optimize module. This study discusses the details of the above mentioned methods. In addition, simulation test of design optimization of a several piping systems were carried out to illustrate the design optimization procedure in detail and to verify the effectiveness of the proposed methodology.