Influenza A(H1N1)pdm09 viruses pose a significant disease burden on children worldwide, with high rates of hospitalization and substantial morbidity and mortality. Outpatient < 18 years of age with upper respiratory infections (URIs) were enrolled through active surveillance at Shanxi Children´s Hospital (SCH) between 7/1/2024 and 6/30/2025. Nasal swabs were collected for the detection of influenza virus and other respiratory pathogens by PCR-based methods. Influenza strains were obtained through in vitro culture, and their antigenic characterization were determined by hemagglutinin-inhibition (HI) assay. Genetic analyses were conducted using next-generation sequencing (NGS), while the fluorescence neuraminidase inhibition assay (FNIA) was employed to ascertain antiviral resistance. A total of 987 throat swab samples were collected. A(H1N1)pdm09 was the main pathogens causing URIs in children during the 2024-2025 influenza season and belongs to the 6B.1A.5a.2a evolutionary branch along with vaccine strains. Four novel HA and six NA non-synonymous substitutions were identified in pH1N1, which are related to antigenic drift and varying degrees of drug resistance, respectively. Three S137P-R142K-V152I-substituted strains were identified as low reactive strains, and strains with T188I, S247N, G249E, I264T, M314I, and K331R substitutions did not demonstrate a significant escalation in drug resistance. Despite the absence of drug-resistant A(H1N1)pdm09 strains in children, the emergence of low-response strains, attributable to mutations associated with antigen drift, necessitates continuous genomic monitoring to ensure preparedness for future seasonal influenza outbreaks.