Employing a retrospective cohort study design, this research utilized the degree of structure variation and grey relational analysis, combined with CPI discount adjustment and the Jonckheere-Terpstra trend test, to evaluate changes in cost composition and resource allocation before and after the implementation of the diagnosis-intervention packet (DIP) at a tertiary hospital in Xiangyang with January 2023 as the cutoff point. Research indicates that in the second year after DIP implementation, the average total cost per case decreased by 24.38% compared to the pre-reform period, with a 60.81% reduction in consumable costs. Consumable cost control showed a one-year delayed response, with the reduction in 2024 exceeding that in 2023 by 27.7 percentage points. From 2020 to 2024, the proportion of drug expenses showed a downward trend, yet maintained the highest correlation (0.982). Meanwhile, the proportions of diagnostic and comprehensive medical service fees increased, respectively, with contribution rates rising. DIP reform drives hospitals to optimize resource allocation through a cost-accounting system, thereby significantly reducing the financial burden on malignant tumor patients. However, an "exceptional case review" mechanism should be established to address the lag in controlling high-cost drug expenses, while preventing clinical risks arising from excessive cost-cutting.