Distance education, an important part of today's education, faces the crucial issue of how to improve the learning quality. Formative assessment is one of the measures to ensure the quality of distance education. By analyzing the problems in the present assessment system and the process of implementation at home and abroad, this thesis puts forward a process of building a formative assessment system on the basis of fuzzy comprehensive evaluation. With the learners as the center, this method supports monitoring and adjustments to be made in the learning process so as to give the learners a direct understanding of their own learning in the course and allow them to make the adjustment for a high quality of learning.