Employing a retrospective cohort study design, this research utilized the Degree of Structure Variation and Grey Correlation Analysis, combined with CPI discount adjustment and the Jonckheere-Terpstra trend test, to evaluate changes in cost structure and resource allocation before and after the implementation of the Diagnosis-Intervention Packet (DIP) (with January 2023 as the cutoff point) at a tertiary hospital in Xiangyang City. Research indicates that in the second year post-DIP implementation, the average total cost per case decreased by 24.38% compared to the pre-reform period (J-T = -83.31,SPS< 0.001), with a 60.81% reduction in material costs. Material cost control showed a one-year delayed response (the reduction in 2024 was 27.7 percentage points greater than in 2023). From 2020 to 2024, the proportion of drug expenses decreased by 2.51 percentage points but exhibited the highest correlation (rS= 0.982), while the proportions of diagnostic and comprehensive medical service fees increased (+2.47%/+2.93%) with rising contribution rates (21.40%/25.35%). DIP reform drives hospitals to optimize resource allocation through a cost-accounting system, significantly reducing the financial burden on malignant tumor patients. However, a "special-case negotiation" mechanism should be established to address the lagged control of high-cost drug expenses, while mitigating clinical risks arising from excessive cost-cutting.