Nonmarine Cretaceous dinoflagellates were recovered in the last decade from a number of basins in northeastern China, which are mostly oil-bearing. These dinoflagellates show close relationship to the water salinity of palaeoenvironments. Two types of dinoflagellate assemblages may be recognized, one from freshwater to slightly brackish and another from slightly brackish to brackish. The former is characterized by the high dominance of ceratioid cysts, particularly species ofNyktericystaandVesperopsiswhereas the composition of the latter is more varied with gonyaulacoid, peridinioid and ceratioid cysts, and varies with the water salinity.