Diagenesis of Carboniferous clastic rocks controlling pore evolution in Tazhong area of Tarim basin was studied quantitatively through core or thin section observation and analysis of data from scanning electron microscope, vitrinite reflectance and inclusion thermometry. The results show that reservoir space of the objective interval is composed of primary intergranular pores and secondary intergranular pores. Mechanical compaction and cementation damaged pores seriously. Compaction decreased the original porosity by 20.7% and cementation only decreased the original porosity by 7.9%. The original porosity was damaged more seriously by compaction than by cementation. Compaction played an important role in the whole process of pore evolution. Dissolution was the only diagenetic action resulting in the improvement of reservoir space and mainly occurred in early diagenetic stage A, the beginning of early diagenetic stage B, the end of the early diagenetic stage B, and the middle diagenetic stage A. In addition, dissolution increased porosity by 3.2%. The research on reservoir diagenesis and the establishment of the porosity evolution model have revealed the stages of pore evolution, which are of great importance to reservoir study and further exploration.