Abstract: The Southwest depression is a secondary structure in the Tarim basin,with an area of 1.225×10⁵ square kilometers,and the main reservoir and production layer within Permo-Carboniferous strata.The major diagenesis of Carboniferous clastic rocks is mechanical compaction,cementation,replacement,dissolution and fracturing.Compaction and cementation resulted in poor reserveoir properties,but dissolution,particularly dissolution during deep burial,improved reservoir properties of clastic reservoirs.Crevice caused by fracturing lead to physical property better in reservoir to a certain extent.