Abstract: Objective To explore the prevalence of central nervous system symptoms of unknown cause(CNSS-UC) and their possible risk factors in urban preschool children.Methods A questionnaire was used to collect relevant information among 661 preschool children in kindergartens in Huangdao district of Qingdao city.The main CNS symptoms,information about dwelling environment,kindergarten environment and outdoor environment,as well as children's personal information,were collected simultaneously.Results The prevalence of CNSS-UC was 26.6%.Multivariate analyses indicated that furniture made from plywood or formed plywood might be adversely associated with CNSS-UC with an odds ratio(OR) and its 95% confidence interval(95% CI) of 2.10(1.29-3.40) and 2.45(1.50-4.00),respectively.Children with high antibiotic use and with a high score for the sensitivity to chemical substances showed a higher risk for CNSS-UC(OR=2.46,95% CI:1.38-4.40 and OR=1.14,95% CI:1.07-1.21).Outdoor environment pollution might also be a possible risk factor for CNSS-UC(OR=1.62,95% CI:1.04-2.53).Cleaning the floor with a wet mop might be a protective factor for CNSS-UC(OR=0.45,95% CI,:0.22-0.92).Conclusion The prevalence of CNSS-UC is relatively high among urban preschool children and the possible risk factors include indoor decoration materials,indoor air particles,traffic pollution,and children's health status.