PBL ( Problem - Based Learning) is a new teaching pattern under the guidance of constructivist theory. It has been an effective learning mechanism to cultivate graduates’innovation ability in the United States. Through clarifying the connotation of PBL pattern,this paper explains the problematic,autonomous,and cooperative characteristics of the teaching method,analyzes the imple- mentation process and evaluation of it,and explores the implementation effectiveness and impact of the method on the innovation ability of American graduates,thus displaying the inspiration of the method to China’s postgraduate education.