This paper displays the effectiveness of applying formative assessment into an interpretation course of two classes of the third-year English majors through a 16-week study in 2014.The participants were at the same interpretation level at the beginning of the research,given the same teaching material,language laboratory and the same teacher during the study.The Experimental Class was evaluated by formative assessment(including In-class Performance,After-class Performance,Final Exam and Assessment Bonus) while the Control Class was evaluated by summative assessment(including Attendance and Final Exam).Results show statistically significant progress of the former over the latter.The better learning effect may be explained by higher motivation and willingness to communicate.