This study used fuzzy analytic hierarchy process (FAHP) to evaluate students’ performance in an environmental economics course under the mode of online and offline blended teaching (OOBT). OOBT was a new teaching mode combining traditional offline teaching with online teaching platform, which could improve students’ after-class learning efficiency and eliminate the limitations of traditional classroom teaching by using an online teaching platform. However, at present, the evaluation methods of OOBT students’ achievement have been scarce. Therefore, this article adopted FAHP to evaluate students’ performance under OOBT. The evaluated course was environmental economics. The results showed that FAHP was not completely dependent on students’ paper scores, and could evaluate students’ scores from group work, attendance, class discussions, and other aspects. The use of OOBT and FAHP led to overall improvement in students’ scores, the average score increased by 7.38, and 81.55% of students were in the middle grade. The case study showed that the integration of FAHP into OOBT could scientifically assign the weight of each evaluation index, make complex performance evaluation problems organized, and fully reflect the comprehensive quality of students. It could also understand students’ dynamics in time, and continuously optimize the course structure according to the feedback information.