Iridium is widely used in low orbit satellite communication system currently, and its airborne transceivers have been using in a variety of civil aviation aircraft. Aimed at the problems that the Iridium satellite system being relatively earlier in design on no consideration of the interference of the newly developed satellite navigation system, and the airborne electronic environment being more and more complex, and the threat to Iridium user link signal being increased, more complete electromagnetic compatibility analysis is needed, a model of receiving Iridium downlink signal is established. The antenna isolation and bit error rate under different interferences are analyzed, and the simulation results are verified by experiments. The effects of wideband and narrowband interference with different frequencies and duty cycles on the quality of downlink signal received by the Iridium airborne equipment are tested, which is in good agreement with the simulation. The results show that under the same power level, the influence of wideband interference is greater than that of narrowband interference. The impact of different types of wideband interference is not much different. The impact of in band and out of band wideband interference is not much different, but the impact of narrowband interference decreases first and then increases. The impact of pulse interference is positively correlated with the duty cycle.