Objective: To investigate parent-child conflict among primary and secondary school students and their parents, and to promote family harmony and mental health of children and adolescents during the COVID-19 pandemic. Methods: An anonymous online survey was completed by 12 711 parents of primary and middle school students during mid-March, 2020. Emotional translation, coping style, parent-child conflict were collected and analyzed by grade. Results: The incidence of parent-child conflict was emotional opposition (62.3%), verbal conflict (52.6%) and physical conflict (20.5%), respectively. About 38.1% of parents and 23.6% of students experienced negative emotions, such as anxiety and anger, and the students used coping styles that were more uniform than those of their parents. About 77.9% of families reported that they experienced different levels of parent-child conflict, which was mainly caused by child learning difficulties(45.6%), daily arrangements(22.1%), and the use of electronic devices(10.2%); compared with the previous year, about 31.4% of families reported an increase in the frequency of parent-child conflicts in the last month. Conclusion Parent-child conflict is highly prevalent in the families of primary and middle school students, and such conflicts were affected by stress-related factors, which included COVID-19. It s necessary to improve the provision of relevant mental health education and psychological assistance.