Objective: Based on the real-world data of medical insurance in City C of Liaoning Province, this study analyzes the characteristics and reform practice of DIP special cases, conducts policy simulation verification, and explores policy optimization and adjustment measures. Methods: We selected 464369 DIP cases in City C, a representative city for DIP payment in Liaoning Province, in 2024. According to the proposed selection rules for high cost cases based on disease value segments, we calculated the number of special cases in each segment and provided distribution simulation results. These results were compared with the city's original special case negotiation policies. Results: The selection rules for high cost cases based on disease value segments demonstrated scientificity. The new rules improved the rationality of the coverage range of special case selection results, better met the requirements of the National Healthcare Security Administration for the proportion of special cases, and facilitated the management of these cases. The selection method in this study can also be implemented in the regions implementing DRG 2.0 version payment of Liaoning Province. Practical experience has proven the rationality and feasibility of this approach. During the transition from DIP 2.0 version to 3.0 version, the experience of segment-based selection of special cases in cities of Liaoning Province can provide useful references for other regions in China.