Abstract: State auditing, internal auditing and social auditing constitute National Science Foundation’s(NSF’S) audit oversight system in U.S., and this three-leveled auditing system strikes a balance between macro and micro. The Office of Inspector General(OIG), as the main body of internal audit, oversees NSF and its grantees on a day-by-day basis and issues audit reports regularly. The connotation and features of this system are analyzed and summarized, its audit practice and impact are introduced, and China could be benefit from the experience of NSF and strengthens auditing supervision for Chinese scientific funds.