Abstract: With the rapid development of the electronics and communication technology, there are growing requirements for ship-borne communication capabilities. And simultaneous communication among multi-frequencies, multi-services, and multiple radios has become the primary requirements for ship-borne communication system. Since electromagnetic interference has a major effect on communication quality, analysis of electromagnetic interference in communication system is imperative for improving commutation quality. As the carrier for electromagnetic wave trans-ceiving, the antenna is one of main focuses during communication system design. This paper analyzes the reciprocal effect between multiple antennas in ship-borne communication system and possible causes that produce interferences. Suggestions are put forward to alleviate electromagnetic interferences in communication system.