Objective: To understand the current situation and associated factors of cellphone usage and addiction among Chinese children and adolescents, to provide reference for effective prevention and intervention of cellphone addiction. Methods: Using a stratified random sampling approach, 11 213 children and adolescents and their parents from 31 provinces, municipalities and autonomous regions in China were recruited and surveyed. Results: The median of daily mobile phone use time among Chinese children and adolescents were 120.00 minutes, as reported by either children or parents. Child s age( β =0.12), hedonic( β =0.11) and social( β =0.09) cellphone use motivations positively related to time spent on cellphone( P <0.01). Cellphone related parental communication( β =-0.06) and knowledge( β =-0.03), as well as cellphone usage on instrumental( β =-0.04) or self representation( β =-0.16) motivation negatively related to time spent on cellphone( P <0.05). Child s age( β =-0.04), cellphone related parental communication( β =-0.09) and awareness( β =-0.14), cellphone use on instrumental motivation( β =-0.22) were negatively associated with cellphone addiction among children and adolescents( P <0.05). Cellphone related parental monitoring( β =0.07), as well as cellphone usage on self representation motivation( β =0.03) or hedonic motivation( β =0.29) positively related to cellphone addiction in children and adolescents( P <0.05). Conclusion Time spent on mobile phone and mobile phone addiction of Chinese children and adolescents are influenced by various internal and external factors, such as the mobile phone use motivation and parenting style.Future school education should help children develop scientific motivation for mobile phone use. Family education should help parents develop positive parenting behaviors such as communication and awareness, so as to reduce the possibility of improper mobile phone use.