The modal analysis and the calculation of dynamic response of the Fenghua Bridge, a new type of long-span steel arch bridge, are carried out using the finite element software ANSYS. Through the on-site testing, the vibration frequency and the change of dynamic displacement response with different weight and speeds are obtained by the DASP data processing software. It is found that the field test results are in consistent with the theoretical results. Firstly, the natural vibration period is 2 ~ 3 times longer than the other ordinary arch bridges, which indicate the bridge structure is stable; Secondly, the dynamic displacement of bridge deck changes in the same direction with weight, while in the opposite direction with speed, and the maximum appears on the midpoint of the middle span; Finally, the maximum dynamic displacement is 11.41mm, which doesn’t exceed the allowable value. So it can be concluded that the bridge is safe under the vehicle-bridge coupling vibration.