Objective: This study assessed the changes in hospitalisation costs before and after the DIP reform in Binzhou City, and compared the differences in the effectiveness of the DIP policy between secondary and lower level and tertiary medical institutions, in order to assess the effectiveness of medical insurance policies based on real-world data and provide evidence for the continuous optimisation of the policy. Methods: The cost data of hospitalised patients with acute subendocardial myocardial infarction as the main diagnosis in Binzhou City from October 2020 to December 2023 were selected to analyse the trend of inpatient costs before and after the implementation of the DIP policy by using the interrupted time-series model, and the extent to which the constituent costs contributed to the changes in the total inpatient costs was explored by Spearman's correlation analysis. Results: The analysis showed that there was no significant change in the total costs and the component costs of inpatients with acute subendocardial myocardial infarction before the reform. After the DIP reform, the total costs showed a trend of decreasing by 2152.25 yuan per month in the short term (P<0.05), and there was no significant change in the long term. However, the total costs of hospitalisation after the DIP reform had the highest correlation with the cost of healthcare services (r=0.881) and the lowest with the cost of consumables (r=0.757). In terms of different levels of medical institutions, there is no significant change in the total cost of secondary and lower medical institutions before the reform, and the instantaneous effect of fee reduction after the reform is obvious, with a monthly reduction of 297.918 yuan in the long term (P<0.05), which is mainly from the examination and test fee, healthcare service fee and consumable fee. There is no significant change in the total cost before and after the reform of the tertiary medical institutions. Conclusion: DIP policy in Binzhou City has a significant effect on the reduction of inpatient costs in the short term, and there is no significant change in the long term. The implementation of DIP policy has optimised the structure of inpatient costs, which reflects the value of healthcare services to a certain extent. The secondary and lower medical institutions are more sensitive to the DIP policy.