Objective To explore the characteristics of cognitive and functional impairment in children with attention-deficit/hyperactivity disorder（ADHD）. Methods A total of 320 children who were diagnosed as ADHD in the Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region between Jan. 2019 and Dec. 2020 and 120normal control children were recruited in the study. The Wechsler intelligence scale for children, fourth edition（WISC-Ⅳ）, Swanson Nolan and Pelham of Chinese version, version Ⅳ scale, parent form（SNAP-Ⅳ）, and Weiss functional impairment rating scale, parent form（WFIRS-P）were used to evaluate the symptoms and functional impairment of children. Results Compared with the control group, the speech comprehension index, perceptual reasoning index, working memory index, processing speed index in WISC-Ⅳ and total intelligence quotient（IQ）in the ADHD group were all significantly lower
（P<0.05）. Compared with the control group, attention deficit, hyperactivity/impulsivity, and oppositional defiant items in SNAP-Ⅳ, and family, earning/school, life skills, self-concept, social activities, and risk-taking activity scores in WFIRS-P in the ADHD group were all significantly higher（P<0.05）. In the ADHD group, the scores of SNAP-Ⅳ and WFIRS-P in the subgroup with IQ<90 were significantly higher than those in the subgroup with IQ≥90（P<0.05）. Conclusion ADHD children have relatively low cognition and functional impairment, and the core symptoms and functional impairment of ADHD are more serious in those with lower intelligence level.