Overall, China has made substantial progress in improving child survival over the past few decades, but a detailed understanding of child mortality trend at local level is limited. This study aimed to present a comprehensive analysis of under-5, infant, and neonatal mortality rates and its trend in Xicheng district of Beijing, China. We used the surveillance data of under-5 children reported by Preventive Health Department of Xicheng District Community Health Service Center from 1991 to 2022. The data was collected based on the Child Death Reporting Card of the Beijing Under-5 Mortality Rate Surveillance Network. Data check was performed by each community health service center and related medical institutions. We extracted data included maternal age, date of death, date of birth, gender, census register, classification of any causes of death, and utilization of healthcare services before death and doubly input it in the Excel 2016 program. Categorization of the causes of death was adapted by the International Categorization of Diseases (ICD-10). Mortality rates and distribution of the leading causes of death were analyzed with descriptive statistics and the Pearson’s Chi-square test using SAS 14.0 software. The Chi-square trend test was used to explore the trends in mortality. Interrupted time series analysis (ITSA) was conducted to assess the impact of the two-child policy on mortality using STATA statistical packages. From 1991 to 2022, totally, there were 166,061 live births and 793 (4.78 ‰) under-5 deaths. The mortality rates of under-5 children, infants and neonates in Xicheng district decreased from 14.75 ‰, 11.25 ‰ and 8.00 ‰ to 1.03 ‰, 0.83 ‰ and 0.41 ‰ respectively. All mortality rates showed an overall significant decline trend (χ2 trend for neonatal = -15.8136, P trend for neonatal