A method for transmitting media stream, comprising: conducting media capability negotiation between a calling terminal and a called terminal according to a link establishment request message transmitted by the calling terminal and a response message transmitted by the called terminal in response to the link establishment request message, and establishing at least two media channels between the calling terminal and the called terminal; transmitting a media stream through a first media channel according to negotiated media capabilities; and when an abnormity of the media stream transmission in the first media channel is detected, selecting another one of the at least two media channels as a second media channel, and switching the media stream from the first media channel to the second media channel for transmission, wherein the first media channel and the second media channel are located in different networks; wherein conducting the media capability negotiation between the calling terminal and the called terminal according to the link establishment request message transmitted by the calling terminal and the response message transmitted by the called terminal in response to the link establishment request message, and establishing the at least two media channels comprises: parsing the link establishment request message initiated by the calling terminal to the called terminal, wherein at least two media channel Internet Protocol, IP, addresses and at least two corresponding media channel port numbers of the calling terminal are carried in the link establishment request message; forwarding the response message transmitted by the called terminal in response to the link establishment request message to the calling terminal, wherein at least two media channel IP addresses and at least two corresponding media channel port numbers of the called terminal are carried in the response message; and establishing the media channels between the calling terminal ports corresponding to the media channel port numbers of the calling terminal and the called terminal ports corresponding to the media channel port numbers of the called terminal. conducting media capability negotiation between a calling terminal and a called terminal according to a link establishment request message transmitted by the calling terminal and a response message transmitted by the called terminal in response to the link establishment request message, and establishing at least two media channels between the calling terminal and the called terminal; transmitting a media stream through a first media channel according to negotiated media capabilities; and when an abnormity of the media stream transmission in the first media channel is detected, selecting another one of the at least two media channels as a second media channel, and switching the media stream from the first media channel to the second media channel for transmission, wherein the first media channel and the second media channel are located in different networks; wherein conducting the media capability negotiation between the calling terminal and the called terminal according to the link establishment request message transmitted by the calling terminal and the response message transmitted by the called terminal in response to the link establishment request message, and establishing the at least two media channels comprises: parsing the link establishment request message initiated by the calling terminal to the called terminal, wherein at least two media channel Internet Protocol, IP, addresses and at least two corresponding media channel port numbers of the calling terminal are carried in the link establishment request message; forwarding the response message transmitted by the called terminal in response to the link establishment request message to the calling terminal, wherein at least two media channel IP addresses and at least two corresponding media channel port numbers of the called terminal are carried in the response message; and establishing the media channels between the calling terminal ports corresponding to the media channel port numbers of the calling terminal and the called terminal ports corresponding to the media channel port numbers of the called terminal. parsing the link establishment request message initiated by the calling terminal to the called terminal, wherein at least two media channel Internet Protocol, IP, addresses and at least two corresponding media channel port numbers of the calling terminal are carried in the link establishment request message; forwarding the response message transmitted by the called terminal in response to the link establishment request message to the calling terminal, wherein at least two media channel IP addresses and at least two corresponding media channel port numbers of the called terminal are carried in the response message; and establishing the media channels between the calling terminal ports corresponding to the media channel port numbers of the calling terminal and the called terminal ports corresponding to the media channel port numbers of the called terminal.