Abstract
This study seeks to investigate the effectiveness of online diagnostic assessment report for teaching and learning. Using U-dig online diagnostic assessment as research material, this empirical study adopts a combination of action research, questionnaire, experiment, interview and document review and the treatment group consists of 25 juniors from English major. Results emerge after analyzing data: online diagnostic assessment report enables teachers to focus on students' weaknesses in reading, subdivide teaching objectives and incorporate high-level cognitive abilities into teaching routine; students are generally satisfied with this feedback report-based teaching mode, the effectiveness of which can then be translated to improvement in students' reading performance; most students express appreciation of the accuracy and precision of the diagnostic report, while some voice uncertainty about how to exploit it to their benefit; statistics of online course learning witness an increase in students' engagement in learning. Findings and implications are also discussed.