Abstract：In this paper, we present an unstructured and adaptive finite element (FE) algorithm for 2D magnetotelluric forward modeling. The unstructured triangular grids can exactly accommodate complex topography and dipping interfaces. Adaptive finite element method can automatically improve mesh design and offer reliable numerical results without significantly increasing the computing time. We compute the magnetotelluric response of a 2D model using the presented FE algorithm, and compare the numerical results to those obtained by the previous FE code with the use of structured rectangular grids. It is verified that the presented algorithm and code are correct and accurate. We finally investigate effects of bathymetry on magnetotelluric responses.