A media stream processing method, a communication system, and a relevant device are disclosed, so as to improve the user experience. The method includes the following steps: a first media receiving device receives media streams, where the media streams include a first media stream and a second media stream; and the first media receiving device processes the first media stream quickly and plays the second media stream normally so that media play progress of the first media receiving device is synchronous with media play progress of the second media receiving device, where the second media receiving device is configured to receive multicast media streams, and the first media receiving device and the second media receiving device are in the same multicast group. A communication system and a relevant device are also disclosed herein. In this way, the user experience is improved.