Abstract: Objective To investigate the prevalence of sleep disorder (SD) and the relationship between SD and attention deficit hyperactivity disorder (ADHD) among preschool children in Weifang city of Shandong province.Methods We selected 935 pre-school children in Weifang city using stratified random sampling and conducted a questionnaire survey between January and December 2016.Information on SD and ADHD of the children were collected from the children's parents and the correlation between SD and ADHD was analyzed.Results The prevalence rate of SD was 44.1% among the children.Common forms of SD were sleep difficulty,enuresis,sweating,and limb shaking,with the prevalence of 19.4%,17.5%,17.0%,and 12.4%,respectively.The prevalence rate of snoring,limb shaking,sleep difficulty,and screaming were significantly higher among the boy children than among the girl children (P<0.05 for all);the prevalence of bruxism was higher among the girl children than among the boy children (P<0.05);the prevalence rate of sweating,limb shaking,enuresis,and screaming were higher among the preschool children aged 3-5 years than among those aged 5-7 years (P<0.05 for all),while the prevalence of snoring,jactitation,and sleep difficulty were higher among the preschool children aged 5-7 years than among those aged 3-5 years (P<0.05 for all).The prevalence of ADHD was significantly higher among the preschool children with SD than among those without SD (χ²=7.240,P=0.007).Conclusion The prevalence of sleep disorder is relatively higher among preschool children in Weifang city and long-term sleep disorder may be a risk factor for attention deficit hyperactivity in preschool children.