Abstract Background Paediatric healthcare is always highlighted in medical and health care system reform in China. Zhejiang Province established a new diagnosis‐related group (DRG) point payment reform in 2020 to regulate provider behaviours and control medical costs. We conducted this study to evaluate impacts of the DRG point payment policy on provider behaviours and resource usage in children's medical services. Methods Data from patients' discharge records from July 2019 to December 2020 in Children's Hospital, Zhejiang University School of Medicine were collected for analysis. We employed the interrupted time series approach to reveal the trend before and after the DRG point payment reform and the difference‐in‐differences analysis to estimate the independent outcome changes attributed to the reform. Results We found that the upward trend of length of stay slightly slowed, and the total costs began to decrease at the post‐policy stage. Although independent effects of the reform were not presented among the whole sample, the length of stay and hospitalisation costs of moderate‐hospital‐stay paediatric patients, non‐surgical patients, and infant patients were found to decrease rapidly after the reform. Conclusion DRG point payments can changed the provider behaviours and eventually reduce healthcare resource usage in children's medical services.