The invention discloses an electromagnetic plane wave sounding method suitable for mountains. The method comprises the steps of: designing a measuring line and a measuring point; determining a puttingstate of an observation device; starting measurement and acquiring and processing electric field and magnetic field data; and drawing images of electric resistivity and a deep section of a measured land. According to the electromagnetic plane wave sounding method suitable for mountains, the electric resistivity sounding data is more correct, the observation horizontal electric fields are along the trend of slopes, the observation magnetic fields are along the tangent directions of the slopes, the observation results are less influenced by terrains and the field operations are simple.