摘要Background Menarche is a substantial milestone of female puberty.Timing of age at menarche is considered the key to understanding the potential linkages with women's health outcomes later in life.This study aimed to explore the secular trends and urban-rural disparities in the median age at menarche among Chinese Han girls from 1985 to 2019.Methods Data were extracted from the 1985,1995,2005,2014,and 2019 Chinese National Surveys on Students'Constitution and Health,which were nationally representative cross-sectional studies,and a total of 173,535 Han girls aged 9-18 years were examined.Girls were asked whether menarche had occurred.The median age at menarche was estimated by probit analysis.Z tests were used to compare the differences between survey years and between urban and rural areas.Results The median age at menarche among Chinese Han girls decreased from 13.37 years in 1985 to 12.00 years in 2019,and the overall decrease was more significant in rural areas(1.77 years)than in urban areas(0.99 years).The average five-year change in the decrease in the median age at menarche showed an accelerating and then slowing pace;and it was observed similarly in both urban and rural areas.The urban-rural disparities shrank from 0.64 years in 1985 to 0.44 years in 1995,then to 0.27 years in 2005,0.24 years in 2014,and finally to-0.14 years in 2019.Conclusions The median age at menarche among Chinese Han girls continued to decline from 1985 to 2019 but at a slow-ing pace in the last five years.Urban-rural disparities gradually narrowed.Sexual and reproductive health education and interventions to prevent the decline in the age of menarche are needed,especially in rural areas.