Abstract: This paper comes up with a new method for identifying the bridge damping ratio based on the vehicle bridge coupling theory under the excitation of a single passing vehicle. Firstly, the integrated inspection vehicle is designed as a single degree of freedom system. The accelerometers integrated on the inspection vehicle are used to collect signals and filter to obtain the bridge frequency response signal of the first mode. The ratio of adjacent peak points is calculated and averaged to obtain the bridge damping ratio of the first mode. Theoretical derivation shows that the inspection vehicle can identify the bridge damping ratio of the first mode when the inspection vehicle parked at any position on the bridge deck. Secondly, considering the influence of the passing vehicle speed, parking position of the inspection vehicle, environmental noise, bridge damping ratio of the first mode and the damping of passing vehicle on the identification results, the effectiveness of this method is verified by the numerical simulation. And comparative studies were also conducted on the classical stochastic subspace method and literature method. Finally, the field test of beam bridge was used to demonstrate the practical applicability of the proposed new method. The research results indicate that the proposed method has no specific requirement on the parking position of the inspection vehicle, avoids the influence of the road roughness on the result of the damping ratio identification, and the passing vehicle damping and speed have no significant influence on the identification of the damping ratio within a certain range, besides, the proposed approach can identify the bridge damping ratio of the first mode with SNR ≥ 30 dB. It has good robustness, simple operation, and does not require bridge closures. It can significantly promote the identification of bridge damping ratio of the first mode in practical engineering.