自從2008年全球經濟衰退以來，歐元區經濟顯著的衰退，特別是歐元區各成員國的經濟表現有明顯的差異。在本文中，我們試就成員國「貿易開放程度」和「財政基本面」這兩個重要特徵，來詮釋歐元區經濟穩定這個議題。在第二章中，我們在貿易開放程度不同的國家下，比較貨幣同盟制度與浮動匯率制度對於負向衝擊產生的影響。我們發現當貨幣當局愈重視產出穩定時，相較於浮動匯率制度，貨幣同盟制度將使產出下降的更多。在第三章中，我們將短期私人債券及長期政府債券引入貨幣同盟的兩國DSGE模型。我們推斷，歐洲央行(ECB)的公共部門債券購買計劃（PSPP），對於不同財政狀況的成員國，有著不對稱的總體經濟影響。在第四章中，我們建立貨幣同盟經濟的最適貨幣政策模型。我們發現成員國間經濟差異，將影響貨幣同盟的整體福利水準。相較於傳統零利率最適貨幣政策文獻，本研究的結果顯示不論是權衡或承諾制度，增加公共部門債券購買將緩和貨幣同盟的經濟波動。 / Since the global recession in 2008, the economic performance of the Euro area has declined significantly. In particular, there have been great differences in the economic performance among member states in the Euro area. In this dissertation, we attempt to address the issue of economic stability by focusing on two key features: the trade openness and the fiscal fundamentals among member states. In Chapter 2, we compare the impacts of the adverse shocks on countries with different degrees of openness under the monetary union regime, and our finding shows that the monetary union will result in a greater decline in output if the monetary authority attaches a higher weight to output stabilization. In Chapter 3, we build a two-country DSGE model representing a monetary union with both short-term and long-term government bonds. We deduce that the ECB’s public sector purchase programme (PSPP) has asymmetric macroeconomic effects on member states under different fiscal fundamentals. In Chapter 4, we set up an optimal monetary policy model of a monetary union. We find that the differences in the economic performance of individual member states will influence the union-wide welfare. Comparing our results with classical literature of optimal monetary policy at zero lower bound, by adding the PSPP, our study indeed reflects lower volatility of the union-wide economy under either discretion or commitment.