Abstract: On the basis of the results of lithostratigraphic, biostratigraphie and chemostratigraphic studies, the base of the Cambrian in southern Liaoning and its adjacent areas is stratigraphieally represented by purplish red terrigenous clastic rocks containing small shelly fossils below the limestone yielding Megapalaeolenus, while the top of the Sinian is marked by a gravity flow sedimentary rock series yielding macroscopic algae. This conclusion changes the previous scheme that the lower boundary of the Cambrian is placed at the bottom of the limestone containing Megapalaeolenus.