Abstract: Measurements of magnetotelluric sounding indicate two highly conductive layers in the crust and upper mantle in the Tangshan area.They lie at a depth of about 20km and 100km,respectively.And they are found deep at southern section and shallow at northern section.The results show that both of the Tangshan earthquake and the Ninghe one occurred along a variable depth-gradient zone for the two layers,with their focal depths no more than those for highly conductive layers in the crust.It has been found in the south of the Tangshan area that a highly conductive layer may be conjectured to be at a depth of 45km,an intermediate one within upper mantle.