A large amount of burrow fossils are found in pelitic siltstone in the middle Changzhougou Formation of the Mesoproterozoic in the Yanshan area. There are preserved comparatively large and vertically straight tubes. Those fossils are the oldest ichnofossils in China, which indicate that the oldest metazoan had appeared before 1800 Ma. The discovery of those fossils is of great significance in probing into the origin and evolution of the Metazoan.