Abstract:The vector and scalar potentials Green’s functions of the Horizontal Electric Dipole (HED) radiation in sea water are derived. The Discrete Complex Image Method (DCIM) which has been used broadly in high frequency domain is introduced into the Extremely Low Frequency (ELF) electromagnetic wave propagation calculation in sea water. The integral path does not hold valid for the ELF situation and the reason can be ascribed to the change of the wave number at different frequency. The new integral path suitable for ELF situation is proposed. The sea environment is modeled as air-sea-sediment three-layer geometry. Generalized Pencil-Of- Function (GPOF) method is used to approximate the integral kernel with exponential summation. The DCIM is employed to obtain spatial domain closed-form Green's functions for the layered model. The electric filed is expressed based on the Mixed-Potential electric field Integral Equation. The results are compared with software FEKO and WHAM. It is safe to conclude that the two-level DCIM approach in this paper is effective and can exhibit better field decay rate at a further distance than WHAM.