This thesis, through a case study over a semester-long period, makes a tentative study into the feasibility of an alternative writing assessment, namely, the controlledwriting portfolio assessment. From the analysis in this thesis, we can find that the experimental writing assessment is both valid and reliable, through which the assessment functions not only as a kind of test to evaluate studentscompetence in writing, but also a diagnostic tool that provides feedback to learners and teachers about the suitability of the instructional materials. Compared with the traditional practice in China, thecontrolledwriting portfolio assessment is believed to be more reliable and could not only better integrate the assessments with classroom instructions but also present a dynamic rather than static picture of students linguistic development.