Abstract: Objective: To analyze the disease group structure and its trends in key departments of large public hospitals using diagnosis related group (DRG) data, explore the key points of intervention and optimization of disease groups in departments, and further promote the rational allocation of department resources. Methods: We retrospectively collected DRG data from two surgical departments in a large public hospital in Beijing from 2017 to 2023. When the case mix index (CMI) of the two surgical departments declined, interventions such as performance appraisal, department education, and hospital publicity were promptly adopted to observe the changes in CMI values and analyze the trends in disease group weights, time consumption index, cost consumption index, and mortality rate in low-risk groups. Results: After the interventions, the proportion of patients with lower-weight diseases, such as major thyroid surgery (KD1), significantly decreased in surgical department 1, while the proportion of patients with higher-weight diseases, such as colorectal malignancy surgery (GB2) and pancreatic malignancy surgery (HB1), increased significantly. In surgical department 2, the proportion of patients with lower-weight diseases, such as chemotherapy (RE1), decreased markedly, while the proportion of patients with higher-weight diseases, including major surgery for malignancy of kidney, ureter, and bladder (LA1), adrenal gland surgery (KC1), surgery for kidney/ureter/bladder except for major malignancy surgery (LB1), and male genital organ malignancy surgery (MA1), increased significantly. Both surgical departments achieved the goal of increasing their CMI values. In terms of efficiency, cost, and quality indicators, the time consumption index and cost consumption index of the two surgical departments were significantly lower than 1, and the mortality rate in low-risk groups was 0. Conclusion: Based on actual conditions and development goals, large public hospitals can achieve improvements in CMI values and optimization of disease group structures through reasonable interventions, thereby enhancing medical efficiency and rational utilization of resources.