The present invention discloses a method for realizing signalling agent based on a media gateway control protocol, which comprises the following steps of: providing an agent equipment between media gateways and a media gateway controller that locate in different networks, the agent equipment providing signalling agent and network address translation between different networks; requesting for registering to the media gateway controller from a media gateway; for a MGCP/MEGACO signalling that is not related to media between the media gateway controller and the media gateway, directly replacing a transaction number by the agent equipment and then forwarding; for a MGCP/MEGACO signalling that is related to media, processing a media identifier correspondingly by the agent equipment and then forwarding. According to the present invention, transparent traversing of MGCP/MEGACO protocol among different networks can be realized to make a media gateway controller control media gateways not matter which network they locate in, in which messages on media gateways are dynamically generated by the agent equipment according to MGCP signallings, and operation maintenance cost decreases.