Answer: Before World War II, the currency exchange rates among western countries were extremely unstable. For their own political and economic interests, countries competed to devalue their currencies and generally strengthened trade control and foreign exchange control, which seriously hindered the development of international trade and the world economy. In May 1944, when the Second World War was coming to an end, in order to adapt to the post-war world economic development, coordinate the interest relations among countries, and also to eliminate exchange rate fluctuations and competitive devaluation under the paper currency system and rebuild the international monetary system, the United Nations convened the "United Nations Monetary and Financial Conference" and established the International Monetary Fund. One of the main tasks of the International Monetary Fund was to establish a post-war fixed exchange rate system. The fixed exchange rate system after World War II is usually called the Bretton Woods system, which is an international monetary system based on the dollar and gold. The advantage of fixed exchange rate system is to reduce the uncertainty of exchange rate fluctuation and promote the stability of price level and inflation expectation. The Bretton Woods system stabilized the post-war international monetary and financial chaos and turmoil, and created a relatively stable monetary and financial environment for all countries in the world. Under the fixed exchange rate system, the fluctuation of foreign exchange rate is not large, which is beneficial to the accounting of import and export trade costs and the calculation of profits, and to the development of international trade and the reconstruction of national economies.