Abstract: Serious EMC(Electro Magnetic Compatibility)issue exists between airborne avionics.For this issue,with the example of the noise jamming in a type of avionics communision system,the generation mechanism of noise signal and its suppression method are detailed researched with theoretical analysis being applied.On the base of these,detailed implementation program for noise jamming suppression is scheduled for avionics communision polluted by 400Hz power supply circuit,and then engineering realization is carried out.Experiment analysis and the effect during mass-producing demonstrate the validation of the mentioned method.