A method for implementing messaging services includes receiving a message body sent by a calling user, determining whether the calling user and a called user are in the same IP Multimedia Subsystem (IMS) domain according to user registration information, and sending the message body to the called user if the calling user and the called user are in the same IMS domain. An IMS messaging service system includes a Message Application Server (MAS), a Call Session Control Function (CSCF) entity, a calling User Equipment (UE) and a called UE. A MAS includes a user registration information storing unit, a receiving unit, and a determining unit adapted to determine whether the calling user and the called user are in the same IMS domain according to the user registration information stored in the user registration information storing unit when the receiving unit receives the message body from the calling user, and a sending unit. According to embodiments of the present disclosure, when the calling user and the called user are in the same IMS domain, the information interaction process and the message body transmission time may be shortened.