OBJECTIVE To multi-dimensionally analyze the characteristics of adverse drug reaction (ADR) reports of medical institutions at different levels by the method of Pareto anlysis to provide accurate data reference for ADR monitoring and safe drug use in clinic thus to better guarantee public medication safety. METHODS ADR reports of 5 tertiary medical institutions, 7 secondary medical institutions, and 12 primary medical institutions and 7 private medical institutions in a district of Shanghai from 2021 to 2023 were retrospectively collected. The characteristics of ADRs were first explored from the time and the medical institution level dimensions. Then, these collected ADR reports were further analyzed using the method of Pareto diagram analysis to identify the mainly and high-frequencily involved drug categories and organ systems. RESULTS A total of 4 279 ADR reports were collected in this study. General ADRs accounted for 85.91% and chemical drug-induced ADRs accouted for 79.48%. From temporal perspective, the number of ADR reports displayed increasing tendency from 2021 to 2023. The elderly were the most involved age groups of human population. Females were more involved than males. From the perspective of medical institution level, ADR reports of tertiary and secondary medical institutions were much more than primary and private medical institutions. In tertiary and secondary medical institutions, the majority of ADRs were induced by anti-infective drugs, anti-tumor and tumor adjuvant drugs, and medication for mental illnesses. Diseases of skin and its subcutaneous tissues, as well as gastrointestinal system were the most common ADR symptoms. In primary medical units, ADRs were most commonly occurred in elderly people, accounting for 81.58%. The majority of ADRs were induced by traditional Chinese medicine (TCM)preparations and cardiovascular drugs, accounting for 29.26% and 23.07%, respectively. Diseases of gastrointestinal symptoms accounted for 34.21% which were the most common ADR symptoms. CONCLUSION Based on the criteria of Pareto classification, there are significant differences in the main drug categories causing ADRs in different levels of medical institutions, but no significant differences were found in the ADR-involved organ systems. Pareto analysis is a reliable menthod to identify drug categories and ADR symptoms needing intensive monitoring. It would facilitate precise adverse reaction monitoring and enhance clinical medication safety.