Aperture coupling was simulated under electromagnetic radiation environment for a helicopter with tangential vector finite element software HFSS.In software HFSS,the size and quantity of the openings needed for external retrofit to the helicopter was simulated,and an emission source interference was used outside the aircraft.Thus it could reflect the impact of electromagnetic radiation to the airborne electronic equipment.Simulation was made to aperture coupling,and the result was compared with the DO-160F standard.The relationship of the radiation energy with frequency and phase,and the radiation energy at different locations,were also studied.Conclusion was obtained through numerical analysis and simulation results,which can be used as a theoretical basis for making openings in helicopter in retrofit.