Provided is a method for transferring messages by establishing a chat room data transfer channel, applicable to an instant message (IM) chat room system based on Session Initiated Protocol (SIP)/Instant Message and Presence Leveraging Extensions (SIMPLE). The method includes the steps of: establishing a first data transfer channel after a negotiation process between the chat room server and an IM server associated with a client, establishing a second data transfer channel after another negotiation process between the IM server and the corresponding client, and transmitting the messages between the client and the chat room server through the first data transfer channel and the second data transfer channel. The method may support a user to join in the chat room and to transmit messages to other users.