The synaeresis cracks of terrigenous fine grained sedimentary rocks are widely developed in the transition phase of lacustrine, ocean and land, and their formation mechanism is of great significance to the study of paleoenvironment, and is also a research hotspot in the field of seismites and microbial sedimentary structures.Methods: Based on the research of synaeresis cracks at home and abroad, the morphological characteristics, genetic mechanism and geological significance of synaeresis cracks are summarized systematically.Results:The results show that: synaeresis cracks are mainly developed in the terrigenous clastic fine- grained sedimentary rocks interbedded with siltstone and clay rock in the transition facies (lacustrine). They usually develop on the bottom of siltstone layer and gradually peak out in the lower clay rock layer. They are filled with silty sand in the form of intestinal, veined or worm- like appearance. It reflects different sedimentary environments. The causes of synaeresis cracks include salinity- related gas condensation, earthquake, storm and microbial mat rupture. synaeresis cracks are important indicators of sedimentary environment, event deposition, and high frequency (lake) regression—(lake) transgression interface interface.Conclusions:The sedimentary facies zone can be indicated according to the morphology and combination of the synaeresis cracks, and the event deposition such as earthquake, storm and gravity flow can be indicated according to the development characteristics of the synaeresis cracks and its associated phenomena. Microbiogenic synaeresis cracks are indicators of sediment exposure and can indicate different levels of (lake) regression—(lake) transgression interface and paleo- sea level changes.