The invention provides a cross-domain multi-media resource identification system and a method thereof. The method includes: the first router transmits the first equipment list of the first LAN to the second router; the second router transmits the second equipment list of the second LAN to the first router; a first electronic device transmits a read request to the second router through the first router when the first electronic device in the first LAN intends to obtain a specific multi-media file of a second electronic device in the second LAN; the second router returns a text message file to the first router; the first router converts the specific internal internet address into an actual external internet address according to the text message file; the first electronic device plays the specific multi-media file according to the actual external internet address.