This paper starts with an analysis of the logics behind the monetary policy of the European Central Bank，and tries to discuss the background and influences of the introduction of its Expanded Asset Purchase Programme. The author believes that the fundamental starting point of the ECB lies not only in stimulating economic growth through the loose monetary policy，but also in generating the smooth functioning of the transmission mechanism of the monetary policy，to guarantee price stability which is the primary task of its monetary policy，thus providing a stable monetary environment for the economic development in the Eurozone.