Abstract: The exploration, sampling and in-situ testing at river beds are one of the most common technical problems associated with hydropower projects in China. The Jinsha River Wudongde Hydropower Station Dam Area has the problems of the riverbed overburden thickness, composition, structure, genetic diversity of hybrid uneven, high cofferdam and deep foundation pit stability. Therefore, we carried out special research work on exploration and sampling technique and in-situ test method. We obtain undisturbed samples with specially developed for single and double tube type hammer. The method makes up for the deficiency of drilling sampling and visualization technology(such as borehole digital TV,hole drilling electromagnetic wave CT) and conventional geophysical methods(such as seismic exploration, borehole acoustic test) combined with the creative development of in situ test. They are comprehensive to identify the composition and structure of river bed overburden and riverbed deep cover. They open up a new path on the layer geological investigation. The engineering properties of layer provides the premise and analysis for the geological high cofferdam and deep foundation pit stability evaluation. The treatment engineering design provides the geological basis with sufficient reliability. They can be used for reference in similar engineering geological investigation.