The existence of center towers is the origin of performance difference between multi-tower suspension bridge and the traditional one, and longitudinal stiffness of the center tower is a decisive factor. Based on the finite element theory, the paper establishes numerical calculation model of multi-tower suspension bridge, and analyzes it’s static and dynamic performance variation by using different longitudinal flexural stiffness. Moreover, the factors that affect center tower stiffness are determined. Referring to judgment standards about usability and structure security given by existing research, the reasonable range of center tower stiffness is established. Besides, the paper tries to ascertain reasonable center tower stiffness by using the static mechanic performance of service phase as judgment standards.