Apply the formative assessment and fuzzy mathematics into college English online learning evaluation

College English Curriculum Requirements demands that we should apply the formative assessment into students' learning evaluation. This paper illustrates that the formative assessment theory and practice, then points out that the formative assessment is a much better assessment in language learning, and it can promote students' language ability mostly, even students' all round-development. Finally, this paper establishes an effective formative assessment index system of college English online learning and examines it with the fuzzy mathematics.