A method, device, and system for carrying a Point of Sale (POS) data service over an IP network are disclosed. A method for carrying a POS data service over an IP network includes receiving, by a home gateway, a number dialed by a user at a POS. When determining that the number dialed at the POS is a POS access code according to configuration information, a call link with a softswitch is set up through Session Initiation Protocol (SIP) signaling interactions and Session Description Protocol (SDP) negotiation is performed with the softswitch. A DSP inside the home gateway is switched from a normal voice mode to a POS data service mode. POS negotiation is performed with a Network Access Server (NAS) connected to a banking center and data services exchanged between the POS and the banking center are transferred after successful negotiation.