中文摘要：

由2007年美国次贷危机引发的金融危机席卷全球，绝大多数经济体受到了不同程度的影响，全球经济呈现衰退趋势。为应对金融危机、防止经济进一步下滑，各国货币管理当局纷纷根据本国特点制定了积极的货币政策。本文选择中国、美国、日本以及欧元区这四个主要经济体作为研究对象，就其在金融危机下采取的货币政策及其效果展开深入分析。我们发现：中国倾向于选择传统的货币政策工具，美国偏重于货币政策工具的创新，日本货币政策更加基于银企密切的关系，而欧洲则偏重于货币政策的国际协调。从整体上看，货币政策对于带动经济走出危机起到了重要作用，不过货币政策效果在各经济体之间还是存在差异的。

英文摘要：

The subprime crisis took place in the America in 2007. Soon it developed into financial crisis, and spread to almost all over the world. In this paper, I choose China, America, Japan and the European Union, discuss the monetary policy they have imposed. As we know, each economy has its own characteristics, so they push different loose monetary policy. In order to prevent the economy from declining persistently, the central bank of every economy has taken traditional monetary policy tools into use, and also invents some new type of tools. To evaluate the effects of their monetary policy, I utilize VAR to see how GDP response to M2. As a whole, monetary policy plays an important role in pulling economy out of crisis.