他國低估匯率造成貿易嚴重扭曲問題近年來越發受到重視，而美國國會為解決主要貿易對手國長期壓抑匯率以提升出口競爭力，導致美國貿易赤字不斷上升之問題，遂陸續提出諸多匯率改革相關法案，期望以具體之制裁手段防止他國持續刻意壓低匯率。 本文先以美國現行法案──1988年匯率與國際經濟政策協調法案作為出發點，探討美國現行法案之不足，以點出美國國會為何認為有於後續改革法案中加入制裁手段之必要，並得出2010年公平貿易貨幣改革法案與2011年貨幣匯率監督改革法案此二法案所提倡之將他國根本性匯率低估或匯率失調情形視為可課徵平衡稅之補貼，為國會多數支持之手段。再以經濟學及國際貿易法學之分析連貫後續討論：匯率低估是否等同對進口課徵關稅並對出口提供補貼？2010年公平貿易貨幣改革法案與2011年貨幣匯率監督改革法案欲將他國根本性匯率低估或匯率失調情形視為可課徵平衡稅之補貼，是否符合WTO有關補貼之規範？前者以Staiger及Sykes兩位學者使用之兩國兩財模型作為討論主軸，後者則以補貼三要件──「財務補助」、「受有利益」及「特定性」加以檢驗。最後皆得出匯率低估僅在特定之情況下始可能構成補貼之結論。 惟在研究過程中，本文發現若僅單憑國際貿易法學之角度去解析匯率低估是否構成補貼，將受法律文字之主觀影響而導致某些謬誤產生。為解決此一問題，本文乃提出以經濟學之分析輔佐國際貿易法裁決之建議，以期能提升國際貿易法裁決之客觀性與公平性。 / The serious trade distortion problem caused by currency undervaluation has given rise to more and more attention. The United States also faces the increasing trade deficit problem caused by some major trading partners that manipulate the value of their currencies in relation to the United States dollar to gain export competitive advantage. The U.S. Congress thus brings up many currency exchange rate reform acts, hoping to use the specific sanction policies to prevent other countries from intentionally depressing exchange rates consistently. This article starts from the U.S. currency act in force──Exchange Rates and International Economic Policy Coordination Act of 1988 to discover the insufficiency in order to point out why the U.S. Congress consider it necessary to put the sanction policies in follow-up currency reform acts. We then conclude that the policies that brought up by "Currency Reform for Fair Trade Act (2010)" and "Currency Exchange Rate Oversight Reform Act of 2011" to deem the "fundamentally undervalued currency" or "misaligned currency" as contervailable subsidies come out in favor of the majority of the U.S. Congress. Follow up we use the analysis of the economies and international trade laws to link the following discussion: is the currency undervaluation equals to import tariffs and export subsidies? Are the policies that deem the "fundamentally undervalued currency" or "misaligned currency" as contervailable subsidies consistent with the WTO’s subsidy regulations? The former one is discussed with the "two countries and two goods model" brought up by Staiger and Sykes while the latter one is examined by three elements: "financial contribution", "benefits" and "specific". The answers are both that the currency undervaluation will be contervailable subsidy in some very specific cases. However, during this research, we find out that if just use the view of international trade laws to analyze whether the currency undervaluation is a contervailable subsidy, we may be affected by the literalism and make mistakes. To solve this problem, we recommend that using the analysis of economies to support the ruling of international trade laws, hoping to increase the objectivity and fairness.