There are provided a home gateway system providing an optical communication packet data interface function and a home broadcast service providing method using the same. The home gateway system is constructed to include a network processor having two Ethernet interfaces connected to a system control processor of a home gateway and an Ethernet switch having an Ethernet multicast traffic processing/IGMP snooping function based on an Ethernet L2 multicast MAC table to thereby simultaneously provide a broadcast service such as a CATV broadcast service, and an Internet data service to a plurality of hosts in a home. In case of a broadcast service, the home gateway system converts a broadcast stream into an IP multicast packet and then processes the broadcast IP multicast packet by an L2 multicast function of an Ethernet switch, thereby making it possible to directly transmit the broadcast IP multicast packet to a host without the help of the control processor.