Under the background of a stable type suspension bridge (A suspension bridge with a inverse-tensional system), the effect of inverse-tensional system for suspension bridge is studied. Using finite element method, three-dimensional finite element model of stable type suspension bridge and a common suspension bridge is established by fish bone model consisting of beam elements respectively. The finite element characteristic equation of two bridges is solved with Block Lanczos method respectively. 20 order eigenpairs of two kind of suspension bridges are obtained. The inherent characteristics of the two type bridges are analyzed comparatively. The results showed that due to the effect of inverse-tensional structures, the overall stiffness of the stable suspension bridge is better than common suspension bridge obviously, which can effectively suppress the torsional vibration of the suspension bridge.