A recording medium and a method for previewing and selecting digital audio/video data unit on the recording medium are provided. The recording medium includes an audio/video pack of the original film, an audio/video pack of the preview film, a background page, and a page control descriptor. After having received a switch button information from a user, a medium reproducing system reads, de-multiplexes, and decodes the information correspond to a specified audio/video pack of the preview film. The medium reproducing system also composes the decoded video data of the background page and the decoded video data of different resolutions to output to a display.