Abstract: Five major stages can be divided regarding formation and evolution of Southwest depression in Tarim basin, ①formation of united paleolandmass in Late Proterozoic; ②rifting of pale- olandmass and subsequent fonning and developing of depression in Early Palaeozoic;③evolution of depression and defferential development of Southwest depression at the eastern and western sides in Late Palaeozoic; ④formation and development of inland basin in Mesozoic; ⑤formaticm and develop- nient ol large lag foreland basin in Cenozoic. Southwest depression is a piedmont one dominated by Cenozoic sediments in terms of the sedimentary and tectonic history.

Key words: Tarim basin, Southwest, Depression, Formation, Evolution, Piedmcait depression