In the exposed bedrock mountain areas of Guizhou Province, most rocks have very high resistivity, and the greatest difficult met by the large-power electrical prospecting lies in the impossibility of inserting the electrode into the rock, hence the electrode grounding is very difficult or even impossible. In order to improve the grounding conditions and realize large-power electric prospecting, the authors, based on summarizing the traditional method for improving grounding resistivity, have summed up the method and technology for improving grounding conditions in exposed bedrock areas. The method is called "water log drowned sheet electrode method". In this method, the closed water-storage space is built at the electric supply station, a certain height of water is stored in the water-storage space, and the metallic sheet electrode is drowned in the water log, thus improving the grounding resistivity. This method is characterized by large grounding area, good contact condition and stable grounding resistivity. Practice shows that this method can obviously improve grounding resistivity, realize large-power current supply exploration, considerably raise the quality of field data, and achieve good application result.