Objective： This study focused on the students’ different decisions on vaccination caused by the contexts of college environment and aimed to use qualitative method to investigate how different fields affect students’ decisions. Methods: Using case contrast x analysis, we carried out in?depth research on class A and B in college S with significant difference in the rate of hepatitis B vaccination （87.5% and 0%, respectively）. Using the convenient sampling method, 6 students from each class were selected to conduct semi-structural interview, and the authoritative representatives at all levels in the field were interviewed, and the data were analyzed with the grounded theory. Results: By comparing two typical cases, this study found that conventional factors such as knowledge about disease, and price of vaccine could not explain the huge gap between the two groups. Instead, a class would form a vaccine?favorable or vaccine?unfavorable field because of differences in information transmission, class atmosphere, as well as curriculum design, and then led college students to make different decisions on vaccination. When the vaccination information passed through different fields, it was influenced by the established characteristic field to guide the individual's behavior decision. Conclusion: We found that flexible management, harmonious atmosphere, communication habits and authoritative media will promote college students to make vaccination decisions. It is suggested to improve the existing vaccination strategy in light of the characteristics of the university field.