The main factor responsible for rich hydrocarbon resources is the good behaviors of reservoirs in South Turgai Basin. An analysis of characteristics, diagenesis and pore type evolution of reservoir rocks shows that diagenesis and pore evolution exerted great effects on the properties of reservoir rocks. Lots of thin sections were analyzed by such means as standard petrographic microscope, X-ray diffraction and scanning electron microscope analysis so as to study the selected samples. Diagenetic complexity suggests that mechanical compaction and pressure solution, miscellaneous filling actions, cementation and replacement led to the decrease of porosity, whereas solution of unsteady minerals resulted in the increase of porosity. The evolution of organic materials and the sequence of clay minerals imply that diagenesis and pore evolution of the sandstone varied obviously with the increasing buried depth: the porosity type was mainly interparticle pores of the primary pore type at the early diagenetic stage, mainly the mixing of the primary and secondary pores at the middle diagenetic stage, and mainly the secondary pores at the late diagenetic stage. A comprehensive evaluation of the reservoirs in South Turgai Basin has led the authors to the conclusion that the Aryskum Formation, the Akshabulak Formation and the Kumkol Formation belong to Class I Reservoir, which may be regarded as the main targets in future prospecting work.