The format of transport stream of high definition television(HDTV) is defined in MPEG－2 system standard ISO/IEC 13818－1.The function of timing information code on synchronizing the video and audio is explained in this paper,and the principle of synchronization of video and audio in HDTV decoder is analyzed.The problems in practical ASIC design, such as the mechanisms of rebuilding of system clock and repeating frame or skipping frame in video and audio, are discussed, a simple non－PLL digital scheme of synchronizing the video and audio is also provided. Update now the method of rebuilding system clock, lagged skipping frame method of synchronization of video and system clock, and digital PLL method of synchronization of audio and system clock are adopted in this scheme. The frame rate of video and warp of audio PCM clock frequency are discussed at last.