Recent developments and important results of magnetotelluric (MT) work in Taiwan are briefly reviewed. As an important intrinsic property of the Earth, the resistivity structure of the Earth is sensitive to the presence of small amounts of conductive minerals, melt or fluids. The latter materials are volumetrically minor, but tectonically important constituents of the Earth's crust and mantle. This paper first reviews the tectonic background of Taiwan in terms of electrical property, and then proposes the possible mechanism of fluids involved during the Chi-Chi earthquake. Important researches regarding both the MT work itself and other geological work, are also suggested in the paper.