Method of transmitting video data in case of channel change in iptv system

A method for transmitting video data in changing a channel in an IPTV(Internet Protocol Television) system is provided to receive an I frame immediately when a channel is changed by transmitting video data by GOP(Group Of Picture) in changing a channel. An STB(Set Top Box) transmits channel request data including changed channel and time information to a video server, which includes a video encoder(822), a video packetizer(824), an audio encoder(812), an audio packetizer(814), and a TS(Transport Stream) multiplexer(830). The video server searches a transmission block corresponding to a transmission file of a channel change request time point and time with reference to a database and transmits it by GOP. The STB receives the transmission block of the changed channel, decodes and displays the same on a screen.