The structural characteristics of four basic types of bridges were summarized: beam bridge, arch bridge, cable-stayed bridge and suspension bridge. The quadrant diagram of bridge type was constructed using orthogonality of beam and pier and symmetry of bridge structure. Basing on the bridge quadrant diagram,①It was proved that there were only five types of basic bridge types. ②The structure and mechanical characteristics of the fifth type of basic bridge structure called as the umbrella bridge were summarized.③The structural features of the umbrella bridge were analyzed and optimized, and the corresponding real bridge after optimization was finally found. The actual bridge not only verified the authenticity of the fifth basic bridge structure derived from the bridge type quadrant diagram, but also proved the correctness of the quadrant diagram of bridge type proposed in the present study. The results of this study provide a useful attempt and discussion for perfecting and guiding the research and development of theoretical bridge.