The embodiment of the invention discloses a media stream proxy method, a voice exchanger and a communication system. The method comprises the following steps: a voice exchanger acquires address information of a called user after being converted by a network address, replaces the address of the called user which is performed and constructed in a media stream message sent by a calling user and port information with the address information of the called user after being converted by the network address, and sends the media stream message sent by the calling user to the called user. Due to the only use of the media stream proxy, the embodiment of the invention can solve the problem of communication isolation, thus simplifying the proxy method. Therefore, the invention can realize the media stream proxy by only using the voice exchanger instead of special proxy equipment, thus solving the problem of communication isolation and reducing the cost.