To realize the rapid inspection of a large amount of small and medium-span bridges， a modal identification method based on the response of moving vehicles is studied. And a moving inspection vehicle with adjustable parameters is proposed. The vehicle parameters are optimized by theoretical derivation， experimental verification， and parameter research. Firstly， an analytical solution of the dynamic response of the specially designed “tractor-double-trailer” vehicle moving along the bridge is derived based on the vehicle-bridge coupled vibration theory. Then， the analytical solution is verified by the numerical results using a self-developed vehicle-bridge coupled analysis program， as well as the field test results of a simply supported beam bridge. Finally， the influence of various factors， such as vehicle parameters， vehicle speed， and bridge parameters， on the identification accuracy is analyzed using the analytical solution. The results show that when the natural frequency of the trailer is 0.8~0.9 （or 1.1~1.2） times the bridge frequency， the performance of the bridge frequency identification using the proposed method is better. It is suggested that the speed of the moving vehicle should not be taken too high. Based on different cross-section areas， cross-section shapes， and spans of the bridge， a reasonable selection of vehicle parameters can improve the accuracy of bridge modal identification. The findings of this paper can provide a good reference for bridge frequency identification using the moving vehicle in practice.