Objective To explore the prevalence and family functions of attention deficit hyperactivity disorder (ADHD)with preschool children in four cities of Fujian province.Methods Totally 1 076 children from 10 kindergartens in four cities of Fujian province were screened randomly by their parents who finished questionnaire ADHD SNAP-Ⅳ first,and then the children who had positive SNAP-Ⅳ were assessed family functions for by Family Assessment Device (FAD).Results There were 474 children screened positively from 1 076 children by SNAP-Ⅳ,and 63 children of them diagnosed by DSM-Ⅴ criteria for ADHD.The rate of positive SNAP-Ⅳ screening was 44% in four cities of Fujian.There were significantly lower scores of communication,roles,affective responsiveness,affective involvement and behavior control subscales,and scores of general function in FAD of preschool ADHD group than that of typically developed children (P<0.01),but there were no significantly differences of scores of subscale of problem-resolve in FAD between two groups.There was no significantly difference of scores of any subscale in FAD between boys and girls (P>0.05),but there were significantly differences of scores of communication,behavior control and general function in FAD among early stage,medium stage and later stage in preschool children (P<0.01).Conclusion We must face the facts of the high prevalence of preschool ADHD and their family faultiness in Fujian.