The Ili area, as a part of the Central Tianshan micro continent, is a inverse triangular area bordered by sutures and zones in the Tianshan belt. Carboniferous volcanic—sedimentary rocks widely outcropping in Ili area is the most direct carrier in the study of Carboniferous basin properties of western Tianshan and Paleozoic orogenic evolution of Tianshan. According to the rock assemblage, stratigraphic sequence, tectonic setting and basin evolution of the Carboniferous volcanic—sedimentary section, we can draw the following conclusions: there is a wide regional angular unconformity between the Lower Carboniferous and its underlying strata(the Precambrian crystalline basemen or pre Carboniferous folded basement). From bottom to top, Carboniferous volcanic—sedimentary rocks can be divided into two sequences respectively corresponding to two cycles of extensional—rift evolution in the basin. SequenceⅠconsists of Dahalajunshan Formation with fan delta facies in the bottom, upward transition as two cycles from volcano explosive facies to effusive facies and Akeshake Formation with fan delta facies in the bottom, upward transition as from shore—shallow sea facies to open platform facies. SequenceⅡconsists of Yishijilike Formation with three cycles by volcano explosive facies to effusive facies and Dongtujinhe Formation with neritic shelf facies. It is believed that the fill sequences in Carboniferous volcanic—sedimentary basin reflected the process of rift basin filling and evolution in post collision extensional setting.