Abstract: Electromagnetic pulses can create large transient voltages and currents by coupling with the cables and equipment in underground engineering, causing electrical system failure or permanent damage. In this paper, an associated Hermite (AH) unconditionally stable finite-difference time-domain (FDTD) method is used to analyze the electromagnetic coupling problem of field-to-ground engineering. Two different tunnel models (circular and rectangular) were established. The AH-FDTD method was used to calculate the field distribution considering depths, geomaterials (dispersion and loss) and oblique incident angles. The effects of coupling field in tunnel engineering under different depths, geomaterials and incident angles are analyzed. It is found that the coupling of the field to the underground tunnel engineering is related to the depth of the tunnel, the dispersion of the geomaterials and the angle of incidence for the plane wave, while the influence from the shape of the tunnel is relatively weak. The proposed analysis method with AH-FDTD method in this paper provides a new way for the study of electromagnetic coupling effect of protection engineering.