Abstract: In our report， in order to obtain the best design from a series of optimized results provided by the optimized programs， a global optimization index （GOI） was proposed， in which Volume reduction ratio （VR） was defined to represent material saving， response index of stress RI（σ） and response index of deformation RI （d） were defined as the values of structural stress. GOI was used to obtain a suitable score for each design solution， the optimum solution with highest score was also obtained. Finally， three bridge cases （the size optimization of steel arch bridge， the topology optimization of concrete shell bridge， and the topology optimization of concrete-steel composite bridge） were analyzed to verify the effectiveness of the optimization index，which provides an intuitive and effective method for designers to find out the optimal design.