Abstract: The research on the development and distribution of the faults in Huizhou sag is conducted by changes of the slips, extensional length, horizons, dip angles of the faults, based on which three grades of the faults are given. The study shows that Grade-II faults have biggest controls on the petroleum accumulation, in which higher enrichment of it could be found along NW faults, but those with too big slips of faults couldn't help the accumulation. The late active faults have bigger controls on the petroleum accumulation in this area.

Key words: Huizhou sag, fault grading, petroleum accumulation