A short message processing method and a relevant system. In one embodiment, a short message service (SMS)-submit message sent by a calling terminal to a mobile switching center (MSC) or service general packet radio service (GPRS) carries an indication that a called terminal does not have an MSISDN, and the SMS-submit message carries a session initiation protocol (SIP) uniform resource identifier (URI) of the called terminal, so that the calling terminal is capable of sending the indication and the SIP URI of the called terminal to an SMS-service center (SMS-SC) via the MSC or SGSN and an SMS-interworking MSC (SMS-IWMSC), and the SMS-SC implements short message communications with the called terminal via an SMS-GMSC and an Internet protocol (IP) short message-gateway (IP-SM-GW).