Left-behind and separated from parents are common among Chinese adolescents and many developing countries, which may cause maltreatment and mental disorders, especially anxiety. Nevertheless, the comprehensive study in the prevalence of childhood maltreatment and its role in anxiety among left-behind adolescents is still insufficient.A nationally representative middle school sample of 32,620 adolescents participated the pen-paper survey regarding demographics, left-behind status and the source of abuse. The Generalized Anxiety Disorder-7 and Chinese version of the Childhood Trauma Questionnaire were used to assess anxiety symptoms and maltreatment experience. The analyses in prevalence, risk factors and mediating effects were preformed in SPSS 27.30,174 valid questionnaires were collected, of which 2748 were left-behind adolescents. 46.4 % of left-behind and 35.6 % of non-left-behind adolescents reported anxiety, and left-behind increased risk of anxiety (OR = 1.180, 95%CI: 1.180-1.286, p < 0.001). In left-behind adolescents, female sex, older age, and maltreatment experience were risk factors of anxiety. Additionally, left-behind adolescents were more likely to suffer serious abuse and all abuse subtypes. The maltreatment almost completely mediated the association between left-behind and anxiety (0.857, 95%bootstrap CI = 0.743, 0.976), of which emotional abuse played the largest role (0.648, CI = 0.547, 0.751), followed by physical neglect, emotional neglect, and sexual abuse.This study revealed the prevalence of anxiety and maltreatment in Chinese left-behind adolescents, and suggested that the maltreatment might significantly mediate the anxiety of left-behind adolescents. This may shed a light on other developing countries where the phenomenon of left-behind adolescents exists.Copyright © 2025. Published by Elsevier B.V.