The Fuyang reservoirs in the Songliao Basin are composed of typical unstable sandstones, with high per- centages of volcanic and feldspar fragments. Therefore, a series of physical and chemical reactions would take place between frameworks and pore water during sedimentation and burial. The geochemical properties of pore fluids are one of the important factors in determining the different diageneses in three dimensions. The origin and evolution of pore water have controlled the diagenesis and evolution of pores of the Fuyang sandstone reser-voirs. Local hydrodynamic units, with different origins and compositions of pore water, may be the main fac-tor, which would have controlled the types of diagenetic facies. The planar division lines of local hydrodynamic units agree well with those of local pore-water geochemical units and diagenetic facies. In the study area, four types of diagenetic facies can be recognized : meteoric water infiltration diagenetic facies, burial water diagenetic facies, mixture water diagenetic facies and paleo-evaporation water diagenetic facies, all of which have differ-ent compositions of autogenetic minerals, pore types and compositions, and different diagenetic charachteristics.