One of the most spectacular features in the Yarlung Zangbo (Indus-Tsangpo) Suture Zone in southern Xizang (Tibet), China, is that it contains pebble-sized to kilometer-scale limestone blocks. Because these blocks are isolated in the surrounding matrix rocks and have no obvious stratigraphical sequences, the interpretations of their origins of the blocks have been the subject of considerable debate for a long time. Studies of the faunas in the limestone blocks suggest that they are all characterized by the mixed characters between the Cathaysian warm-water faunas and the Gondwanan cold-water faunas. The faunas in the limestone blocks in the Yarlung Zangbo Suture Zone, as a whole, are similar one another, and therefore may represent a generally similar sedimentary environment and paleogeographical setting. These faunas range from the late Early Permian to Changhsingian in the limestone blocks and can be largely divided into two types based on corals, fusulinids and brachiopods. One is characterized by the dominance of solitary corals, absence of fusulinids and more cold-water brachiopods, and probably represents a paleogeographical setting closer to the peri-Gondwanan margin. The other is characterized by the presence of compound corals, fusulinids and more warm-water brachiopods and therefore indicates a paleogeographical setting closer to the Lhasa Block. The limestone blocks are mostly composed of reddish or gray massive bioclastic limestone and commonly faulted with volcanic rocks or have a volcanic basement. Therefore, it is most likely that these blocks represent some carbonate deposits on the outer shelves of the peri-Gondwanan region or seamount deposits in the initial rifting stage of the Neo-Tethys, but subsequently sandwiched into the Mesozoic/Cenozoic deposits during the collision between the Indian and Eurasian Plates.