Objectives To understand the status of positive affect (PA) and negative affect (NA) on university and college students, and to explore the determinants during the COVID-19 outbreak. Methods Our data were from network-based survey, and 17,876 participants completed the questionnaire. t test, one-way ANOVA and multiple linear regression model were performed using PANAS (Positive and Negative Affect Schedule) score as the dependent variable. Results Of 17,876 participants, the mean score of PA was 25.5 ± 7.3, while NA was 19.1 ± 7.1. Multiple linear regression models showed that there are some common determinants of PA and NA, such as education, health literacy on communicable diseases, satisfaction with measures for epidemic prevention and control, risk of infection, impact of the outbreak on daily life, sleep duration and frequency of hand washing in the past 2 weeks. Besides, whether the student is a medical major and whether outing in the past 2 weeks were specific determinants of PA, and frequency of masks wearing was specific determinant of NA. Conclusions The outbreak of COVID-19 is detrimental to university and college students' affect. During the outbreak response, we should strengthen the guidance and regulation for negative affect and pay attention to improving the positive affect of university and college students.