The embodiment of the invention provides a method and device for transmitting a message, and relates to the field of communication. The method and device for transmitting the message are used for further relieving the shortage of IPv4 addresses. The method for transmitting the message comprises the steps that an IP address and MAC address information of a target terminal are obtained through a server, whether the IP address of the target terminal and an IP address of a first terminal are the same is determined, when it is determined that the IP address of the target terminal and the IP address of the first terminal are the same, whether a matching item matched with the MAC address information of the target terminal exists in a stored MAC forwarding table is determined according to the MAC address information of the target terminal, if it is determined that the matching item exists, an MAC address of the first terminal serves a source MAC address in message header data and an MAC address of a source host, and an MAC address of the target terminal serves a target MAC address in the message header data and an MAC address of a target host and is added to the message header data of the message, and the message is transmitted to an interchanger.