A method, performed by a home gateway, for carrying a Point of Sale, POS, data service over an Internet Protocol, IP, network, comprising: receiving 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, setting up (103, 403) a call link with a softswitch (204, 802) through Session Initiation Protocol, SIP, signaling interactions and performing Session Description Protocol, SDP, negotiation with the softswitch (204, 802) to negotiate an operation of switching to a POS data service mode; switching a Digital Signal Processor, DSP, inside the home gateway (201, 801) from a normal voice mode to the POS data service mode after successful SDP negotiation between the home gateway (201, 801) and the softswitch (204, 802); and performing a POS negotiation with a Network Access Server, NAS, (206, 804) connected to a banking center and transferring (108, 409) data services exchanged between the POS and the banking center after successful POS negotiation; wherein the performing SDP negotiation with the softswitch to negotiate an operation of switching to a POS data service mode comprises: initiating, by the home gateway (201, 801), a call to the softswitch (204, 802) via SIP signaling, including an X-pos media attribute indicating that what is negotiated is not a normal voice mode but switching to the POS data service mode in an SDP message carried in the SIP signaling, and receiving a SIP message returned by the softswitch (204, 802) comprising a SDP message which also carries a X-pos media attribute and information for switching into POS data service mode, to determine that the SDP negotiation is successful. receiving 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, setting up (103, 403) a call link with a softswitch (204, 802) through Session Initiation Protocol, SIP, signaling interactions and performing Session Description Protocol, SDP, negotiation with the softswitch (204, 802) to negotiate an operation of switching to a POS data service mode; switching a Digital Signal Processor, DSP, inside the home gateway (201, 801) from a normal voice mode to the POS data service mode after successful SDP negotiation between the home gateway (201, 801) and the softswitch (204, 802); and performing a POS negotiation with a Network Access Server, NAS, (206, 804) connected to a banking center and transferring (108, 409) data services exchanged between the POS and the banking center after successful POS negotiation; wherein the performing SDP negotiation with the softswitch to negotiate an operation of switching to a POS data service mode comprises: initiating, by the home gateway (201, 801), a call to the softswitch (204, 802) via SIP signaling, including an X-pos media attribute indicating that what is negotiated is not a normal voice mode but switching to the POS data service mode in an SDP message carried in the SIP signaling, and receiving a SIP message returned by the softswitch (204, 802) comprising a SDP message which also carries a X-pos media attribute and information for switching into POS data service mode, to determine that the SDP negotiation is successful. initiating, by the home gateway (201, 801), a call to the softswitch (204, 802) via SIP signaling, including an X-pos media attribute indicating that what is negotiated is not a normal voice mode but switching to the POS data service mode in an SDP message carried in the SIP signaling, and receiving a SIP message returned by the softswitch (204, 802) comprising a SDP message which also carries a X-pos media attribute and information for switching into POS data service mode, to determine that the SDP negotiation is successful.