Abstract: From bear-source Maxwell equation, the paper, in accordance with line-source non-even Helmholtz equation under conditions of two-dimension topography,defined the boundary conditions. With the use of boundary element method, E. M. frequency sounding curves affected by undulate topography are computed, and the converted to the topography effects on frequency sounding curves of two-dimension topography by way of point-source equator device. The rule of that topography affects frequency sounding curves is sumed, and correcting method is found out.