On the basis of core observation and high density slice identification, the authors consider that Es₃^x-Es₄^s mudstone in Jiyang depression is mainly controlled by sedimentation and diagenesis. The composition and structure types are mainly controlled by sedimentation, whereas crystal texture characteristics are mainly controlled by diagenesis. According to the genesis and degree of recrystallization of calcite, combined with the mineral composition and structure characteristics, the Paleogene mudstone in Jiyang depression can be divided into three types, i.e., sedimentation-controlled type, sedimentation and diagenesis-controlled type and diagenesis-controlled type. The sedimentation-controlled type is the most widely distributed type which includes various types of lithofaces and whose structural characteristics reflect the formation environment. Sedimentation and diagenesis-controlled type mainly appears as laminated rock facies consisting of interlayered laminae of the argillaceous and granular crystallized calcite. Diagenesis-controlled type is characterized by column or fiber-column calcite crystals in the veined or lenticular forms perpendicular to the bedding plane. The diagenesis-controlled type and sedimentation and diagenesis-controlled type are closely related to Oil and gas in shale, and they are the most favorable genetic lithofacies.