According to the characteristics of classroom teaching for infrastructure engineering specialty in research universities, a teaching quality assessment index system is established from the students’ teaching evaluation. And then, the relationship of the relative membership between mood operator and quantitative scale is used to determine the index weight. Finally, the variable fuzzy sets and assessment model are put into use to evaluate classroom teaching quality quantitatively. A case study is testified to prove the variable principle and calculating steps of the fuzzy sets and the feasibility and effectiveness of this model as well.