Abstract：As a new type of bridge, vibration characteristics of multi-tower self-anchored suspension bridge(MSSB) is quite different from traditional suspension bridge. For equivalent stiffness of cables in main span is relatively small and stiffness of middle towers is relatively large, the influence of tower stiffness on vertical frequency of MSSB usually can not be ignored. In this paper, the three-tower self-anchored suspension bridge(TSSB) was taken as research object, which is the simplest type of MSSB. Considering tower stiffness infleuence, frequency formulas for 1st anti-symmetric and symmetric vertical vibration modes of TSSB were derived by the Rayleigh method. The accuracy of proposed formulas are checked by modal test result and numerical simulation result respectively. These formulas can be appropriate to calculate vertical frequency for TSSB, and can further be promote to frequency calculation for MSSB.