Objective: To explore the changes and influencing factors of the cost structure of hospitalized patients in FM19 group after the reform of DRG payment method, and to provide references for the reasonable management and control of such medical ex- penses. Methods: The information of patients in FM19 group and the use of high-value consumables in 8 DRG pilot hospitals in Yan- tai city were analyzed by statistical description. The main types and directions of cost changes were analyzed by structural variation analysis. Results: The number of inpatients increased, and the average hospitalization cost and consumables cost decreased obviously. From 2019 to 2021, the structural variation of the average inpatient hospitalization cost was 46.50%, and the consumables cost, opera- tion cost and treatment cost are the main items affecting the change of hospitalization cost, with a cumulative contribution rate of 84.24%. Conclusion: The cost of hospitalized patients in FM19 patients decreased significantly and the cost structure was gradually rationalized, but the increase of service facility cost reflecting the labor value of medical personnel was limited. Meanwhile, in order to avoid the abuse of high-value consumables, the fund supervision should be strengthened continuously.