Abstract: The dynamic responses under an ambient vibration for eight half-through and through concrete-filled steel tubular (CFST) arch bridges are measured. The Stochastic Subspace Identification (SSI) method presented by Katayama is used for experimental modal analyses, and the feasibility of this method is verified by comparing with the results obtained by the Maximum Entropy Method. Compared with the experimental modal analysis by SSI method, the correctness of theoretic modal analysis by the finite element method is confirmed. The influence of some parameters, such as the arch main span, cross section and deck system, is discussed on the in-plane vibration properties of CFST arch bridges. The limitation of the statistical approximate formula for the in-plane first frequencies of CFST arch bridges is pointed out, and the static method based on the Rayleigh energy method is presented, which can predict and check in-plane low frequencies of half-through and through CFST arch bridges.