We carry out three-dimensional(3-D) modeling of frequency electromagnetic sounding in layered anisotropic earth using integral equation method. A integral equation formulation is derived based on modified Green's operator with norm less or equal to one. The integral equation is convergent for any conductivity distribution and frequency if iterative solvers are used. An optimal choice method on initial guess for iterative solvers is introduced. It improves computational efficiency of 3-D modeling of frequency electromagnetic sounding significantly. Apparent resistivity responses of 3-D axial frequency electromagnetic sounding are considered in multilayered anisotropic earth.