Bridge dynamics is an important topic in the development of the modern Bridges. It not only can reflect the mechanical performance of the bridge structure under the action of vehicle load, but also reveals system influences on the bridge structure under seismic action. But in order to supplement the shortage of the pure theoretical mechanics model, we need to do some tests to improve the research that is also the most reliable method. Illustrated by the example of a viaduct (continuous steel box girder-bridge) in Taiyuan, the testing span is loaded and tested. We analyze the structure using the bridge calculation common software Midas. The existing Bridge in dynamic test loads is analyzed to research that if their vibration characteristics and dynamic response and dynamic performance can meet the requirements of normal use.