Provided are an IPTV service system and a method thereof. The IPTV service system includes: a headend, a set-top box, and a plurality of multicast routers. The headend assigns a multicast group address for each channel and assigns a source address for each PID with respect to an MPEG-TS and packetizes the MPEG-TS into a plurality of packet streams. The set-top box identifies a user-selected channel and the necessary elementary streams in the MPEG-TS for the selected channel, and requests selective reception of only packet streams corresponding to the selected channel and the necessary elementary streams from the plurality of packet streams. The plurality of multicast routers form a multicast path between the headend and the set-top box. Accordingly, while services such as a multi-angle service, a multi-lingual service, a mosaic EPG service, and a personalized EPG service are realized in one multicast control method together with viewing of a general broadcasting channel, efficient use of bandwidth can be achieved.