Since 1980, experts of the Institute of Geophysical and Geochemical Exploration have constructed some 6 800 km of deep magnetotelluric sounding profiles in such areas as Qinghai-Tibet, Sichuan-Yunnan, South China, Gansu, Xinjiang, Inner Mongolia, Shanxi, Song-Liao, middle and lower reaches of the Yangtze River and Qinling Mountains, found out electric structure of the crust and the upper mantle along these profiles, studied relationships between electric units and geologic-tectonic units, and probed into the causes for the formation of the low-resistivity layers detected in the crust and the upper mantle. On the basis of the available deep magnetotelluric sounding data, the continental electrical maps of China have been compliled. It is thus known that the continental lithosphere of China has an average thickness of 100～200 km, thinning in the east and thickening in the west. Using electrical resistivities of rocks measured under high temperature and pressure, the researchers have roughly determined material constitutuents of the lithosphere along the profiles.