Combining core description，thin sections analysis，whole-rock X-ray diffraction and scanning electron micros copy technologies，the characteristics of mineral composition of fine-grained sedimentary rocks，sedimentary structure and laminations in the lower Es3 member in the Dongying sag were described in detail，by which lithofacies of fine-grained rocks were classified and their vertical evolution characteristics were analyzed using a case from the lower Es3 member drilled by Well FY1. The results show that the fine-grained rocks in the lower Es3 member is characterized by complex and variable mineral composition，frequent and weak bottom current reworking and abundant laminations. Based on the mineral composition and sedimentary structure，there are eleven types of lithofacies in the study area，and seven of them are mainly developed，which are parallel-laminated clay stone，interbedded calcareous limestone，parallel-laminated limestone，nonparallel-laminated limestone，parallel-laminated mixed sedimentary rock，nonparallel-laminated mixed sedimentary rock and massive mixed sedimentary rock. Their development environment are different obviously.The distribution of fine sedimentary facies is controlled by paleo-water depth and paleoclimate. The parallel-laminated clay stone are developed mainly in deep water in dry and cold reducing environment. Interbedded limestone develops when the paleoclimate changes from dry and cold to warm and wet. Parallel-laminated limestone develops in wide and deep water when the paleoclimate is semi-warm and wet. Nonparallel-laminated limestone develops when the paleoclimate becomes the warmest and wettest and the bottom current develops. Parallel-laminated mixed sedimentary rock develops when the water becomes shallower with unstable water delimitation and the paleoclimate becomes drier and colder. And the nonparallel-laminated mixed sedimentary rock will develop if there are bottom current. The massive mixed sedimentary rock develops in semi oxidation and reduction environment.