Family harmony is a state of good relations among family members, smooth communication, mutual support and reasonable conflict resolution. Maintaining good family harmony is important for improving individual well-being, promoting physical and mental health, and fostering social stability and development. The factors affecting the developmental changes of family harmony are currently under-explored, and our study followed the same cohort of university students for more than three years in the context of the Covid-19 pandemic, thus revealing the impact of the pandemic on college students' experience of family harmony. 215 (M = 18.87, SD = 0.92), 211 (M = 18.88, SD = 0.92), and 57 (M = 21.70, SD = 0.82) participants completed the College Students' Experience of Family Harmony Questionnaire (CSEFHQ) in early December 2019 (before the pandemic), March 2020 (at the stage of the outbreak of COVID-19), and April 2023 (after the end of the pandemic). Using mixed regression models, significant differences in college students' experience of family harmony were found at three time points. Our study shows that college students' experience of family harmony is significantly lower over time, from before the epidemic to during the epidemic to after the end of the epidemic. It is evident that the Covid-19 pandemic had a significant negative impact on family harmony and that the impact persisted after the end of the epidemic to the extent that the sense of family harmony after the end of the epidemic was not only lower than before the epidemic but also lower than during the epidemic. The study suggests that individuals need to make efforts to establish good communication with family members, increase opportunities to spend time together, and support each other in order to overcome the negative effects of the Covid-19 pandemic on family harmony.