In this paper, the author put forward a double model to solve the method of electrical impedance imaging system.In the treatment of the forward problem, provides a fine cylinder model; In the treatment of the inverse problem, provides a relatively rough 3d model of cylinder.The two models is through the corresponding mapping formula for finite element unit and deficient detailed finite element unit conversion.To find the mapping system model transformation, this paper puts forward the dual model is established by sparse matrix P which is the mapping relationship.Finally using the reconstruction algorithm of electrical impedance imaging, proves the double model system.Through the computer simulation and using modified Laplace GuassNewton reconstruction algorithm can get impedance reconstruction images clearly.