Upper Cretaceous sandstones in the middle of Changling Depression of Songliao Basin mainly belong to lithic arkose, which experienced mechanical compaction, carbonate cementation, clay mineral cementation, silicate cementation, silicic cementation, dissolution of unstable components and local metasomatism.A variety of pore types in studied region include intergranular pores, intragranular pores, moldic pores, as well as a negligible amount of micro-pores and oversized pores. Based on the diagenetic events, the diagenetic stages of the studied area are diversified from the early eodiagenesis B to the mesodiagenesis B, with the principal diagenetic stage being the mesodiagenesis A. The classification of diagenetic facies in the area is discussed on the basis of sedimentary facies and diagenesis.