Based on the theory of plate tectonics, combining with the isotopic dating of ophiolite, igneous and volcanics, geochemical test, rare earth element analyze and seismic interpretation, this paper studies the pre-Carboniferous tectonics and sedimentary formation of the south edge of the Tarim Basin and proves that there exists the Kunlun Ocean under tensional tectonics during the Sinian and Cambrian in the south edge of the Tarim Plate. After that, due to the collision orogenesis, there formed the peripheral foreland basin in the south edge of Tarim. The Upper Silurian and Devonian molasses sedimentary system superposed on the Sinian and Middle Silurian passive margin flysch sedimentary system and formed the bivariate structure of the foreland basin. And at the same time, based on the field geology and seismic interpretation, we have identified that the formation of the Silurian and Devonian have the character of half deposit which shows thick in the south area and thin in the north, and the pre-Carboniferous thrust compression tectonics remained in the foreland thrust belt, which further demonstrates that there existed the Silurian and Devonian peripheral foreland basin on the south edge of the Tarim Basin.