Abstract: Natural vibration tests of single-cable-stayed beam and double-cables-stayed beam are conducted. Models of the two structures are established by the finite element method for the global dynamic analysis of cable-stayed bridges, and their accuracy is verified by the test results. According to the finite element analysis of single-cable-stayed beams to four-cables-stayed beams, the influence of the existence and number of cables on in-plane natural frequency is large, but that on out-of-plane natural frequency is small. Because cables support the beam vertically, the increase in the number of cables will lead to an increase in the in-plane natural frequency of cable-stayed beam structures. By assuming the cable's vertical support to be elastic and considering the effect of the horizontal component of cable force on the axial force of the beam, the frequency equation and mode function of in-plane natural vibration for multi-cables-stayed beams are derived. The validity and applicability of the simplified formulas are verified by finite element analyses.