審計制度是民主國家政治過程中重要的一環，其理論基礎建構在制衡原理上。一個國家審計功能之強弱對該國行政體系進行政策規劃與制定、資源分配與管理、政策執行與評估、類政效率與浪費有密切的關係，而審計機關居於監督與評估之關鍵地位，由於審計制度對政府公共政策運作績效居於評估的實質地位，使得立法機關能在行政機關編列預算時，能有預先審查資料的基礎，而在施政後又能瞭解其具體的績效。本文即在分析美國會計總署從帳冊審計邁向計畫評估的功能。 全文說明了美國會計總署六位審計長的貢獻，並分析其組織與決策系統，以及計畫評估與運作程序，並對政府政策與計畫實際接受審計監督的運作情形加以剖白。

　　　　　This article is a structural and functional study of the U.S. General Accounting Office from its establishment in 1921 to the present time. The research focuses on how the organization was created and on what bases the institution is founded. Both theoretical analysis and practical development are emphasized. From its early book auditing role, the GAO has entered into an era of program evaluation. For major contributions and achievements, six leading Comptroller Generals are examined and discussed: J. R. McCarl, L. C. Warren, Joseph Campbell, E. B. Staats, C. A. Bowsher, and D. M. Walker. The organizational structure and decision making system of the GAO are also emphazed in this paper. Finally, program evaluation and operational procedures of the American auditing system are analyzed in considerable detail. In conclusion, the author argues that the GAO has played an important role in maintaining the mechanism of the system of check and blances in American governmental operation. In particular, the GAO is a very effective watchdog over the spending power of the Executive Branch.