【Objective】 To investigate the sleep conditions and correlative factors of children 3~6 years old children in Nanjing. 【Method】 1 327 children aged 3~6 years old were randomly selected for investigation in Nanjing. 【Results】 There was a higher prevalenee rate of sleep disorders in children in Nanjing city than the level of investigations in other cities,it was 52.67%.Among their symptoms of sleep disorder,hyperhidrosis was 34.51%,molar teeth 14.47%,restless sleep 10.78%,sleep snoring 10.32%,night talking 9.34%,mouth breathing 6.41%,limber spasm 4.60%,sleep long time in daytime and less in night 2.03%,screeching or crying during sleeping 2.03%,going to sleep early1.96%,choke gargling 1.28%,night awakenings 0.98%,limber spasm 0.38%,sleep apnea 0.23%,sleep walking 0.08%.The prevalences of hyperhidrosis,sleep long time in daytime and less in night of boys were larger than girls.The prevalence of night talking of girls was larger than boys.The main factors those affected the sleep disorders were 5 including the having diseases,feelings before sleep,sleep time,sleep posture,playing games outside.There were many factors those affected the sleep problems of children including children's age,heredity and environmental factors.