The lithosphere-asthenosphere boundary (LAB) is one of the main boundary of the earths interior.Magnetotelluric (MT) sounding is the most effective method for investigation of the electrical structure of the crust and upper mantle of the earth.LAB is feasibly detectable by using long-period MT data.The high-quality MT data had been acquired on grid of 4°×4° in South China under SinoProbe-01-03 project.We inverted the average apparent resistivity calculated from the off-diagonal elements by using one-dimension Occams method.We interpret the recovered 1D geoelectric structure by classifying the lithosphere of the South China as five different types: the craton type, the tectonic boundary type, the moderate reformed lithosphere type, the strong reformed lithosphere type, the orogenic belt type.Our results show that the lithosphere of the South China is thinner in the south and north regions, and thicker in the middle region; while the lithosphere of the South China is unevenly reformed in the east region.The results in present study are different from that of the previously published literatures, in most of which indicated that the significant characteristic of the lithospheric thickness of the South China is thinning from west to east.Our results support that the lithosphere of the South China is mechanically strong and hence stable.The tectonic extension occurred since the Late Mesozoic may limitedly reform the lithosphere of the South China, and the most possible reforming mechanism is by hot asthenospheric materials diapiring and underplating.