Abstract: The oil that wax content is over 8% is called high-wax oil. Traditionally, it is considered that wax is normal alkane with high molecular weight, and it is originated from higher plant. Recent-year studies demonstrate that wax consists of not only high-molecularweight normal alkane, but also isoalkane, naphthene and olefin; and the origin of wax is not only from high plant, but also lower hydrobiont and lacustrine algae which are as important contributors to the wax. The wax content of crude oil in Nanyang sag ranges from 40% to 60%, and the type of organic matter is dominated by Type IIB~III. It is suggested that the high-wax oil is mainly originated from terrestrial higher plant, while lower hydrobiont is accidental.

Key words: Nanyang sag, high-wax oil, genesis, higher plant, lower hydrobiont