COVID-19 has posed unprecedented challenges to the mental health of college students worldwide. We examined the trends in students' stress levels during and after China's first wave of COVID-19 outbreaks by analyzing their demographics, behavior, mental health status, career confidence, and Chinese Perceived Stress Scale (CPSS) scores. Our findings indicate an increase in students' stress levels since the COVID-19 onset, with more students experiencing higher stress levels after the first outbreak than during it (OR = 2.03, 95% CI 1.79, 2.30). Several factors were identified as being associated with higher CPSS scores, including higher class levels, residence in rural or town areas, low family income, and lack of familiarity with COVID-19, among others. Our study highlighted the urgency of developing and implementing effective strategies to cope with students' stress during and after a global pandemic.