In order to solve the multi-objective fuzzy optimization problems of ship structures, two approaches, known as the Maximum Level Method and the Linear Weighted Sum Method, based on the different forms of fuzzy decision-making are presented. In these methods, the membership functions are constructed for the subsets of the fuzzy goals subject to the fuzzy constraints, and then the multi-objective fuzzy optimization problem is transformed into the single-objective ordinary optimization problem, which can be solved by using nonlinear programming techniques. The proposed approaches are illustrated by two numerical examples in the application of ship structural design.