Under the conditions of the parallel-runway at airports, the impact of the electromagnetic interference caused by an Airbus_A320 with the fuselage parallel to the runway and the tail toward localizer antenna on the localizer beam of the ILS (Instrument Landing System) is analyzed in this paper. Firstly, the model of the electromagnetic environment of the localizer is established, including the localizer antenna and its associated transmitter, the numerical aircraft scattering model, and the receiver and subsequent data processing. And then the simulated data are calculated by means of the computer. Finally, according to the simulated data, the parameters impacting much on the multipath interference will be found and the solution will be advised to reduce this interference. And it will be much useful to find out the optimized routes of the operating aircrafts with the help of the data.