Abstract: There is a rockfill dam with clay facing in Guangdong, and its earth blanket′s state such as compactness and uniformity is important. Transient Rayleigh wave can be used to inspect the loose layer and leakage anomaly region of the earth dam. The vibroseis source can arouse precise and controllable high frequency seismic wave so as to improve seismic solution for shallow seismic prospecting. Field test is carried out with vibroseis seismic prospecting system developed by our lab in Nanshui dam. Frequency dispersion,attenuation coefficient,energy and wave speed are analyzed as the testing data. It is indicated that the speed of some spots is low,and that the vibroseis system can do shallow seismic prospecting effectively.