In a modern capitalistic nation, a central bank is a key institution among national financial systems that monopolizes money issuance and controls money supply. After Lehman Brothers` filing for bankruptcy protection in September 2008, major countries such as the United States of America and the Great Britain intensified the roles of financial stability in their central banks through financial reforms. The Bank of Korea has striven actively to respond to the financial and economic turmoil through diverse policy instruments such as reduction of base rate, encouragement of flows of funds to financial markets, stabilization of foreign exchange and foreign currency funding markets, and so forth. But the Bank of Korea did not have powers enough to overcome the financial and economic turmoil. So there was a lively discussions in the National Assembly on the amendment of the Bank of Korea Act in order to strengthen the functions of the Bank such as financial stability and banking supervision. This paper is to analyze an overview of banking supervision, the relationship between a central bank and the function of banking supervision, the contents and suggestions of financial reforms in such countries as USA and England and EU, the changes of banking supervision in the Bank of Korea, and the discussions and evaluations of the amendment of the Bank of Korea Act after the global financial and economic turmoil since 2008. Major Revisions to the Bank of Korea Act are specifying responsibility for financial stability, enhancing access to information, improving emergency liquidity support facilities, improving the reserve requirement system, strengthening currency management, increasing retention of net profit, and enhancing accountability. As the importance of macroprudential policies has grown globally - based on lessons drawn from the 2008 global financial crisis - the revision of the Bank of Korea Act is directed toward strengthening the financial stability role of the central bank in line with this trend. It will consequently contribute to elevating the international profiles of both Korea and its central bank, by enhancing Korean financial system stability while at the same time heightening Korea`s external credibility.