One of the most important subjects in designing long-span bridges is to ensure aerodynamic stability of superstructure. In order to improve the aerodynamic stability, various researches were conducted and authors proposed a new type super-long span bridge which is excellent in economical efficiency and aerodynamic stability. This bridge has structural characteristics both of cable stayed bridge and suspension bridge. And the stiffening girder consists of slotted box girder part for the center of the main span to improve aerodynamic stability and standard 1-box girder part near the main towers to reduce construction cost of substructure. In this paper, main results of frame structural analysis and wind tunnel test of section model which were conducted in order to determine the structural dimensions of this new bridge with main span of 2.8km, are outlined first. Then the outline of design of 1/125 scale full model and the main results of the wind tunnel tests are described.