The invention discloses a method and system for realizing transmission of message between an extended processor and a switch chip. The switch chip amends the destination MAC of the received first message to be transmitted to the extended processor as the first destination MAC, and then transmit the first message to the extended processor, wherein the first destination MAC corresponds to the service physical port of the switch chip for receiving the first message; the extended processor can resolve the first destination MAC to learn that the first message comes from the service physical port. The method and system of the invention can realize transmission of message between the extended processor and the switch chip.