Abstract: Because of the weakness in determining of the mud layer waving situation in traditional drilling exploration, we always use the shallow seismic reflected wave method in some retaining dike to determin the mud layer's waving situation. From the reflectional geophysical prospecting image of this water area, we know that there's a absolute line between slit layer and clay layer. There's a clear reflective wave in 30m,and it can be easily seem the moving situation of the bedrock surface. Compared with the drilling information, geophysical prospecting is more accuracy, and meets the requirment of this project. It shows that the shallow seismic reflected wave method is the fast, efficient new method in water project geophysical prospecting. It has the broad application prospects in a variety of geotechnical engineering investigation.