Many reefs of the Late Paleozoic have been discovered recently in the Hinggan-Inner Mongolia area.These reefs clearly are geographically extensive,and possess distinctive features and well-developed reef-facies.They have been found to contain five reef-building communities and were constructed in four periods.Colonial coral-algal reefs at Aohan and Chifeng represent a warm shallow-sea in the Carboniferous.Different reefs in the Xiwu Banner were formed in three periods:early Late Carboniferous,late Late Carboniferous and Early Permian.These reefs were built in warm sea conditions.Their buildup types include colonial coral frameworks,algae-buildings and lime-mud mounds.Bryozoan reefs in the Zhalaite and Dongwu banners were built in the late Middle Permian and thrived in a cold shallow-sea.All reefs grew independently on two kinds of sedimentary platforms,carbonate and carbonate-clastic mixed platforms.Four reef-forming periods occurred later from south to north,along a collisional course between the North China Plate and the Siberian Plate.These reefs can be arranged into three ’reef-links’ or reef zones that extend along plate margins.Among these,the Aohan-Chifeng reef-link indicates a northern margin of the North China Plate,the Zhalaite-Dongwu reef-link marks a southern margin of the Siberian Plate,and the Xiwu-Beishan reef-link reflects the former existence of some inter-plates.The strata of each reef-facies are thick and contain rich asphalt deposits.Overlapping and heteropic layers are very thick and contain dark oil/gas-rich horizons;TOC analyses verify that most of these are good hydrocarbon source rocks.This study shows that the study area is an excellent candidate for oil-gas exploration. Many reefs of the Late Paleozoic have been discovered recently in the Hinggan-Inner Mongolia area. The reefs clearly are geographically extensive, and possess distinctive features and well-developed reef-facies. They have been found to contain five reef-building communities and were Constructed in four periods.Colonial coral-algal reefs at Aohan and Chifeng represent a warm shallow-sea in the Carboniferous. Different reefs in the Xiwu Banner were formed in three periods: early Late Carboniferous, late Late Carboniferous and Early Permian.These reefs were built in warm sea conditions. Their buildup types include colonial coral frameworks, algae-buildings and lime-mud mounds.Bryozoan reefs in the Zhalaite and Dongwu banners were built in the late Middle Permian and thrived in a cold shallow-sea. All reefs grew independently on two kinds of sedimentary platforms, carbonate and carbonate-clastic mixed platforms. Focus reef-forming both occurred later from south to north, along a collisional course between the North China Plate and the Siberian Plate. The reefs can be arranged into three ’reef-links’ or reef zones that extend along the plate margins. Among these, the Aohan-Chifeng reef-link indicates a northern margin of the North China Plate , the Zhalaite-Dongwu reef-link marks a southern margin of the Siberian Plate, and the Xiwu-Beishan reef-link reflects the former existence of some inter-plates. The strata of each reef-facies are thick and contain rich asphalt deposits. Overlapping and heteropic layers are very thick and contain dark oil / gas-rich horizons; TOC analyzes verify that most of these are good hydrocarbon source rocks.This study shows that the study area is an excellent candidate for oil-gas exploration.