Based on the data of drilling cores, casting thin sections and physical properties, the characteristics of diagenesis, diagenetic facies and its influences on diagenetic traps of red beds reservoirs of the first member of Kongdian fromation ( Ek1 ) and the lower fourth member of Shahejie formation ( Es4^ x ) of Paleogene in Dongying depression were studied. The results show that compaction is moderate to strong, and cements are mainly carbonate, ferro-carbonate, gypsum, anhydrite and au- thigenic quartz. Dissolution mainly occurs as dissolving of feldspar, quartz and carbonate cement. Cementation is strong at the boundary belt and pinchout belt of sandstones and is weak at the middle part of sandstones. Strength of cementation in middle part of sandstones increases gradually from the lower part to the upper part of fault block. The early cementation re-strained the compaction. Strength of dissolution increases gradually with the increasing of distance to interface of mudstone and sandstone and decreases gradually from the lower part to the upper part of fault block. Five types of diagenetic facies oc- cur mainly: compaction diagenetic facies, dense carbonate cementation diagenetic facies, dense sulfate cementation diagenet-ic facies, medium compaction-dissolution diagenetic facies and strong compaction-dissolution diagenetic facies. The reservoir physical properties and effective reservoirs content of different diagenetic facies are obviously different. The space allocation of diagenetic facies controls the development of diagenetic traps in red beds.