In order to promote the development of basic bridge types，the structural characteristic of four basic types of bridges were summarized. Those were the beam bridge，arch bridge，cable-stayed bridge and suspension bridge. The quadrant diagram of bridge was constructed using orthogonality of beam and pier and symmetry of bridge structure.The results show，it was proved that there were only five types of basic bridge. The structure and mechanical characteristic of the fifth type of basic bridge structure was summarized as the umbrella bridge. The structural feature of the umbrella bridge was analyzed and optimized. The corresponding real bridge after optimization was then 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 research results provide a basis for researching to improve and perfect the bridge type.