A method for implementing a Packet Switched domain (PS) short message service (SMS) includes: after receiving request message containing an SMS-only indication transmitted by a user equipment, a mobility management entity enquiring subscription information of the user equipment from a home subscriber server, and receiving the subscription information of the user equipment returned by the home subscriber server; and when the mobility management entity supports the PS SMS and the subscription information supports the PS SMS, the mobility management entity transmitting request acceptance message to the user equipment, receiving and transmitting an SMS between the mobility management entity and the user equipment through a Packet Switched domain. Embodiments of the present document further provide a system for implementing a PS SMS and a user equipment. By means of the scheme of the present document, the PS SMS can be implemented in an EPS system.