There has been a strong controversy about the origins of the limestone landforms on Tibet plateau for a long time. In this paper, intensive field surveys, together with dating of the cave secondary calcite crystals, has revealed that the current limestone karst landforms on the plateau was originated from later erosion of the Tertiary underground karst. During the Pleistocene inter-glacial epoch, the tropical-subtropical type of karstification continued at least on the southern part of the plateau. This kind of karst landforms is called the old karst in this paper. However, during the Pleistocene glacieal epoch, the melting water of the Pleistocene glaciers can form some small-scale karst caves along the margin of the glacial valley in the limestone mountains. The parallel-oriented karrens, with a depth no more than 10 cm, on present limestone surface are the results of the Holocene erosion. These karrens are named modern karst. The karst landforms on the Tibetan plateau have undergone a distinctive change from lower altitude and latitude to higher altitude and latitude since the Late Cenozoic.