The integrity and measurement accuracy of dam vibration information (such as frequency) are usually affected by environmental background noise, such as flood discharge noises, and measuring point location. In light of this problem, a data-level fusion method based on variance dedication rate (VDR) of the dam structural vibration response is proposed. The fusion coefficients of vibration signals are dynamically allocated with the defined VDR of the vibration signals. The data from the numeric simulation tests of the arch dam and the prototype′s vibration signal show that the weak high-frequency signal of the structural vibration is mined, and the overall dynamic characteristics of the dam structure are comprehensively retained. Compared with the traditional correlation function fusion method, this method has better prospects in terms of the completeness and accuracy of the extraction of dynamic characteristics in the high arch dam.