As a new bridge system, mechanics behavior study on long-span multi-tower suspension is also very deficiency. The existence of center towers is the origin of performance difference between multi-tower suspension bridge and the traditional one. Based on the Midas/Civil platform, the paper takes a three tower suspension bridge as project reference, establishes finite element models of suspension bridge, which the main span is longer than one kilometer and towers from two to seven. Moreover, the structural property is analyzed separately, which bending moment and displacement effect of girder and tower along with the tower number changes is considered. Natural frequency differences of the model bridges are also paid attention on.