ObjectivesSince COVID-19 first appeared in Wuhan, China, in December 2019, the disease has spread rapidly across the country. To reduce the spread of infection, schools including kindergartens were closed. Prolonged home confinement can affect children’s behaviour. Therefore, we investigated the change of preschoolers’ total daily screen time during the COVID-19 lockdown in China.Design, setting and participantsIn the parental survey, 1121 preschoolers, whose parents or grandparents completed an online survey from 1 June 2020 to 5 June 2020, were enrolled.Primary outcomeTotal daily screen time. Multivariable modelling was performed to identify factors associated with increased screen time.ResultsThe results showed that preschoolers’ total daily screen time during lockdown(median 2.5 hours, IQR 2.5 hours) was significantly longer than it was before lockdown (median 1.5 hours, IQR 1.0 hour). Older age (OR 1.26, 95% CI 1.07 to 1.48), higher annual household income (OR 1.18, 95% CI 1.04 to 1.34),and decrease of moderate-vigorous physical activity (OR 1.41, 95% CI 1.20 to 1.66) were independently associated with increased screen time.ConclusionsPreschoolers’ total daily screen time significantly increased during lockdown.