英语写作一直是初中英语学习者的薄弱项，究其原因，写作评价方式在很大程度上制约了学生英语写作能力的提高。在以往的英语写作教学中，教师多使用终结性评价，这种评价方式，重结果、轻过程，重知识、轻能力。而《义务教育英语课程标准》（2011）提倡在英语教学中要使用形成性评价来监控和促进教与学的过程，实现形成性评价与终结性评价相结合。因此作为一线英语教师我们要思考如何将形成性评价有效地运用于自己的教学中，引导学生自主学习，提高学生的英语学习的能力。本研究通过实验探索形成性评价在英语教学中的具体方式，了解档案袋评价是否能够激发学生对英语写作的兴趣，并在此基础上提高学生的英语写作能力。其次，了解运用档案袋是否能培养学生的自我反思和自我评价能力。在研究中制作调查问卷和对学生进行访谈了解学生的英语写作状况；选择写作试题对学生进行研究前后的写作测试。采用问卷调查、访谈、实验等研究方法，利用调查问卷、评价量表等研究工具在所教班级的英语写作教学中使用档案袋评价方式。 通过对比分析实验前后的调查问卷和前后测的数据，明显看出学生对英语写作的态度有所改善，兴趣有所增强，写作能力也有所提高。从数据中可以得出以下结论：档案袋评价能够激发学生对英语写作的兴趣，并在此基础上提高学生的英语写作能力。其次，运用档案袋能培养学生的自我反思和自我评价能力。

English writing is a weak part for learners of junior high school in China. When it comes to the causes of this phenomenon, it is mostly the ways of evaluation in writing teaching that block the improvement of the writing ability. In English writing teaching, teachers used summative assessment only, which pays more attention to the results of learning but not the process. The New English Curriculum Standard advocates that formative assessment should be used to monitor and improve the process of teaching and learning in order to realize combination of formative and summative assessment. So as an English teacher we should think over how to apply formative assessment to our teaching in order to guide students to learn automatically and improve their learning ability effectively. The purpose of the study is to find out if portfolio assessment can motivate students’ interest in English writing and improve their writing ability. What’s more, the study attempts to know about if writing portfolio can develop students’ ability of self-reflection and self-evaluation. So in this study, portfolio assessment is applied to English writing teaching, using questionnaires, evaluation tables as instruments and doing questionnaires, interviewing and making experiments as research methods. Data is collected by literature research, questionnaire survey, experiment and interview. Through the comparison of the data collected from the questionnaires and the tests before and after the experiment, the author comes to the conclusion that portfolio assessment can develop students’ ability of self-reflection and self-evaluation and it can greatly arouse students’ interest in English writing, change students’ attitude to writing and as a result, their writing ability can be greatly improved.