A data loading method is for an audio/video playback system. The method is used for playing an audio/video data stored in a storage medium. The audio/video data comprises a plurality of audio/video segments and a plurality of navigation data corresponding to the audio/video segments. The method comprises loading only a portion of a corresponding navigation data into a memory while an audio/video segment is played. The playing of the audio/video segments is controlled by the loaded part of the navigation data.