OBJECTIVE To describe the incidence of inappropriate medication prescription and adverse drug reactions between 2020 and 2021 in our hospital, providing new strategies to reduce medication errors in pediatrics and providing reference for pharmacovigilance. METHODS A graded response system based on hospital information system (HIS), medication instructions and clinical guideline was constructed to provide a scientific basis for clinical intervention and management by pharmacists. The frequency, types and distribution of inappropriate medication prescription were collected by retrieving electronic medical record. By frequency analysis, composition ratio analysis and other methods, the safety, rationality, and necessity of pre-prescription review system were evaluated. RESULTS The most common types of errors identified included inappropriate refills, incorrect dose/frequency, inappropriate drug-drug interaction, off-label medication, and quantity prescribed. After the pre-prescription review system was constructed, the amounts of inappropriate medication prescription (level 5-7) in outpatient and inpatient department were decreased by 63.4% and 64.7%, respectively (P<0.05). By stratified analysis, the amounts of inappropriate medication prescription (level 5-7) in neonatal intensive care unit and cardiac intensive care unit were declined markedly (P<0.05). In addition, the incidence of adverse drug reaction was declined notably, especially the general adverse drug reactions and severe adverse drug reactions, which were decreased by 22.7% and 60.0%, respectively (P<0.05). One year after the pre-prescription review system put into service, a retrospective review of inappropriate prescriptions (level 6-7) demonstrated a 71.6%-79.2% successful intervention rate by the system. CONCLUSION The application of pre-prescription review system improved the quality and efficiency of prescription review, and it also provide opportunities for pharmacists to ensure safe and optimal prescribing.