Objective To analyse the sleep time,the prevalence and the risk factors of sleep disorders in children of 3~6 years old in Nanjing,and to provide evidence for the prevention and intervention of sleep disorders. Method A total of 1 122 children of children of 3~6 years old were selected by a stratified cluster sampling method from Nanjing city,and the parents were surveyed with Children's Sleep Habits Qusetionnaire(CSHQ). Results The mean of total sleep time of 3~6 years old children were remarkably shorter compared with the typical sleep time of Western children of the same age.Sleep time were gradually reduced with age,and the children's sleep times in one day of eaeh age groups were different remarkly but same for boys and girls.The incidence of sleep disorder was 35.7%,the incidence of hyperhidrosis was 34%,molar teeth 13.9%,sleep snoring 10.5%,restless sleep 10.2%,night talking 8.9%,mouth breathing 6.4%,etc.The main factors that affected the sleep time of children were children's age,parenting style,family pattern and the related symptoms of sleep disorder.The main factors that affected the sleep disorder were gender,health status of children,emotion before sleeping,sleep habit of children and the sleep time in a day,etc. Conclusions The total sleep time of preschool children is relatively less in Nanjing,and the prevalence of sleep disorders is higher compared to the existing data,which should pay a great attention.The concrete methods of prevention and treatment about the disease should be researched in the future.