Abstract: To explore the sedimentary environment and control factors of fine-grained sedimentary rocks (FGSR) is beneficial to grasp the characteristics and distribution of mud shale reservoirs from the origin, thus more effectively guiding the exploration of unconventional hydrocarbons. Based on well cores, thin sections, X-ray diffraction and geochemical analysis, it is found that among the sedimentary environment elements of fine-grained sedimentary rocks in the upper fourth Member of Dongying sag, climate, water depth and reducibility have four stages of change, showing an overall cyclicity. In the second stage, the salinity was gradually reduced from the abnormally high value as influenced by transgression. The major factors controlling the development of FGSR include provenance, climate, water physical-chemical conditions, tectonism and emergencies. The parent rocks in the study area are consisted of metamorphic rocks, sedimentary rocks (carbonate rocks, quartz sandstones and etc.) and igneous rocks, providing clay minerals, carbonates and silts as the material basis for FGSR after weathering. The cyclicity of climate and water physical-chemical conditions leads to vertical regular changes in FGSR. Tectonism exerts certain influences on the distribution of FGSR though controlling the sedimentary facies. Meanwhile, the development of FGSR is influenced by emergencies (turbidity current and etc.).