In the process of concrete dam body vibration testing, need reasonable decorate on sensor nodes. However, in the process of dam body vibration signal transfer, for routing the dependence of the single sensor network node is too big, cause uneven load arrangement process, detection accuracy. Put forward a kind of sensor network node layout method based on density automatic adjustment, and apply to the dam vibration tests. Using the node initial coordinates of arch dam. Using the theory of vibration feedback judge the node density on the dam body, adjust the optimal position of the node according to the judgment. The experimental results show that the large dam vibration tests using this method, can improve the detection of vibration time, improve the efficiency of detection.