The boundary-element method is used to model the 2D terrain effect on the magnetotelluric (MT) field. Firstly, the boundary-value problem of a 2D magnetotelluric field is transfored into an integral equation problem by using Green's theorem. Then the boundary-element method is used to solve the integral equation andto obt ain the MT field and its normal derivative on the terrain. From these values, the apparent resistivity can be calculated. Compared with the finite-element method, the boundary-element method is simpler in element division and the initital data preparation. The configuration of a terrain dividedby the boundary-element method is more consistenr with the practical terrain. the method proposed in this paper can be run on a microcomputer, so that it can be used in the field.