The invention discloses an ultra-wideband (UWB) positioning system, UWB base stations (BSs), UWB tags and the operation methods thereof. Because the present invention uses a server aware of the positions of all BSs to determine the BSs that performs distance measurement, and the server assigns different time slots to each BS that performs distance measurement, the present invention can avoid collisions between the BSs in the process of distance measurement. Furthermore, because the tag can select a specific time slot to access the UWB positioning system by monitoring the UWB signals in the air, the present invention can reduce collisions between the tags. By carefully planning the system frames and subframes of the time division multiplexing system, and sophisticatedly arranging the operation timings of the BSs and the tags, the present invention provides practical and stable UWB positioning system, BSs, and tags.